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.
66830 vulnerabilities reference this CWE, most recent first.
GHSA-2MRQ-W8PV-5PVQ
Vulnerability from github – Published: 2024-02-02 18:10 – Updated: 2024-02-12 15:34Impact
There is a potential for a mutation XSS (mXSS) vulnerability in AntiSamy caused by flawed parsing of the HTML being sanitized. To be subject to this vulnerability the preserveComments directive must be enabled in your policy file. As a result, certain crafty inputs can result in elements in comment tags being interpreted as executable when using AntiSamy's sanitized output.
Patches
Patched in AntiSamy 1.7.5 and later. This is due to parsing behavior in the neko-htmlunit dependency, just by updating to a newer version the issue was solved. See important remediation details in the reference given below.
Workarounds
If you cannot upgrade to a fixed version of the library, the following mitigation can be applied until you can upgrade: Manually edit your AntiSamy policy file (e.g., antisamy.xml) by deleting the preserveComments directive or setting its value to false, if present.
As the previously mentioned policy settings are preconditions for the mXSS attack to work, changing them as recommended should be sufficient to protect you against this vulnerability when using a vulnerable version of this library. However, the existing bug would still be present in the parser dependency (neko-htmlunit) and therefore in AntiSamy. The safety of this workaround relies on configurations that may change in the future and don't address the root cause of the vulnerability. As such, it is strongly recommended to upgrade to a fixed version of AntiSamy.
For more information
If you have any questions or comments about this advisory:
Email one of the project co-leaders, listed on the OWASP AntiSamy project page, under "Leaders".
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.7.4"
},
"package": {
"ecosystem": "Maven",
"name": "org.owasp.antisamy:antisamy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.7.5"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2024-23635"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2024-02-02T18:10:04Z",
"nvd_published_at": "2024-02-02T17:15:11Z",
"severity": "MODERATE"
},
"details": "# Impact\n\nThere is a potential for a mutation XSS (mXSS) vulnerability in AntiSamy caused by flawed parsing of the HTML being sanitized. To be subject to this vulnerability the `preserveComments` directive must be enabled in your policy file. As a result, certain crafty inputs can result in elements in comment tags being interpreted as executable when using AntiSamy\u0027s sanitized output.\n\n# Patches\n\nPatched in AntiSamy 1.7.5 and later. This is due to parsing behavior in the [neko-htmlunit](https://github.com/HtmlUnit/htmlunit-neko) dependency, just by updating to a newer version the issue was solved. See important remediation details in the reference given below.\n\n# Workarounds\n\nIf you cannot upgrade to a fixed version of the library, the following mitigation can be applied until you can upgrade: Manually edit your AntiSamy policy file (e.g., antisamy.xml) by deleting the `preserveComments` directive or setting its value to `false`, if present.\n\nAs the previously mentioned policy settings are preconditions for the mXSS attack to work, changing them as recommended should be sufficient to protect you against this vulnerability when using a vulnerable version of this library. However, the existing bug would still be present in the parser dependency (neko-htmlunit) and therefore in AntiSamy. The safety of this workaround relies on configurations that may change in the future and don\u0027t address the root cause of the vulnerability. As such, it is strongly recommended to upgrade to a fixed version of AntiSamy.\n\n# For more information\n\nIf you have any questions or comments about this advisory:\n\nEmail one of the project co-leaders, listed on the [OWASP AntiSamy project](https://owasp.org/www-project-antisamy/) page, under \"Leaders\".\n",
"id": "GHSA-2mrq-w8pv-5pvq",
"modified": "2024-02-12T15:34:23Z",
"published": "2024-02-02T18:10:04Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/nahsra/antisamy/security/advisories/GHSA-2mrq-w8pv-5pvq"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-23635"
},
{
"type": "WEB",
"url": "https://github.com/nahsra/antisamy/commit/12a2e31d3855430c119480655c2bbbbb79a66ecd"
},
{
"type": "WEB",
"url": "https://github.com/nahsra/antisamy/commit/3e84410ed06ab67f0a4cc3183c67528210f4847d"
},
{
"type": "PACKAGE",
"url": "https://github.com/nahsra/antisamy"
}
],
"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": "Malicious input can provoke XSS when preserving comments"
}
GHSA-2MRV-XV63-4P6G
Vulnerability from github – Published: 2025-09-10 18:30 – Updated: 2025-10-29 18:30Pega Platform versions 7.1.0 to Infinity 24.2.2 are affected by a Stored XSS issue in a user interface component. Requires a high privileged user with a developer role.
{
"affected": [],
"aliases": [
"CVE-2025-8681"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-10T16:15:42Z",
"severity": "MODERATE"
},
"details": "Pega Platform versions 7.1.0 to Infinity 24.2.2 are affected by a Stored XSS issue in a user interface component. \u00a0Requires a high privileged user with a developer role.",
"id": "GHSA-2mrv-xv63-4p6g",
"modified": "2025-10-29T18:30:31Z",
"published": "2025-09-10T18:30:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-8681"
},
{
"type": "WEB",
"url": "https://support.pega.com/support-doc/pega-security-advisory-g25-vulnerability-remediation-note"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2MV3-MWWF-9MRV
Vulnerability from github – Published: 2023-03-11 21:30 – Updated: 2023-03-15 21:30A vulnerability was found in dd32 Debug Bar Plugin up to 0.8. It has been declared as problematic. Affected by this vulnerability is the function render of the file panels/class-debug-bar-queries.php. The manipulation leads to cross site scripting. The attack can be launched remotely. Upgrading to version 0.8.1 is able to address this issue. The name of the patch is 0842af8f8a556bc3e39b9ef758173b0a8a9ccbfc. It is recommended to upgrade the affected component. The associated identifier of this vulnerability is VDB-222739.
{
"affected": [],
"aliases": [
"CVE-2013-10021"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-03-11T21:15:00Z",
"severity": "MODERATE"
},
"details": "A vulnerability was found in dd32 Debug Bar Plugin up to 0.8. It has been declared as problematic. Affected by this vulnerability is the function render of the file panels/class-debug-bar-queries.php. The manipulation leads to cross site scripting. The attack can be launched remotely. Upgrading to version 0.8.1 is able to address this issue. The name of the patch is 0842af8f8a556bc3e39b9ef758173b0a8a9ccbfc. It is recommended to upgrade the affected component. The associated identifier of this vulnerability is VDB-222739.",
"id": "GHSA-2mv3-mwwf-9mrv",
"modified": "2023-03-15T21:30:25Z",
"published": "2023-03-11T21:30:14Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2013-10021"
},
{
"type": "WEB",
"url": "https://github.com/dd32/debug-bar/commit/0842af8f8a556bc3e39b9ef758173b0a8a9ccbfc"
},
{
"type": "WEB",
"url": "https://github.com/dd32/debug-bar/releases/tag/0.8.1"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.222739"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.222739"
}
],
"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"
}
]
}
GHSA-2MVG-5FWF-W2PP
Vulnerability from github – Published: 2022-05-17 01:33 – Updated: 2022-05-17 01:33Multiple cross-site scripting (XSS) vulnerabilities in IBM TRIRIGA Application Platform 2.x and 3.x before 3.3.1.1, and 8, allow remote authenticated users to inject arbitrary web script or HTML via (1) unspecified input to WebProcess.srv, (2) unspecified input to html/en/default/actionHandler/queryHandler.jsp, or (3) unspecified input in a portalSectionId action to html/en/default/reportTemplate/hGridTopQuery.jsp.
{
"affected": [],
"aliases": [
"CVE-2013-4003"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2013-08-29T12:07:00Z",
"severity": "LOW"
},
"details": "Multiple cross-site scripting (XSS) vulnerabilities in IBM TRIRIGA Application Platform 2.x and 3.x before 3.3.1.1, and 8, allow remote authenticated users to inject arbitrary web script or HTML via (1) unspecified input to WebProcess.srv, (2) unspecified input to html/en/default/actionHandler/queryHandler.jsp, or (3) unspecified input in a portalSectionId action to html/en/default/reportTemplate/hGridTopQuery.jsp.",
"id": "GHSA-2mvg-5fwf-w2pp",
"modified": "2022-05-17T01:33:52Z",
"published": "2022-05-17T01:33:52Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2013-4003"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/85266"
},
{
"type": "WEB",
"url": "https://www.ibm.com/connections/blogs/PSIRT/entry/security_bulletin_ibm_tririga_application_platform_has_potential_cross_site_scripting_vulnerabilities_in_various_url_s"
},
{
"type": "WEB",
"url": "http://www-01.ibm.com/support/docview.wss?uid=swg21646694"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-2MVG-C6MG-3Q63
Vulnerability from github – Published: 2022-05-13 01:08 – Updated: 2023-10-10 14:41concrete5 8.1.0 places incorrect trust in the HTTP Host header during caching, if the administrator did not define a "canonical" URL on installation of concrete5 using the "Advanced Options" settings. Remote attackers can make a GET request with any domain name in the Host header. This is stored and allows for arbitrary domains to be set for certain links displayed to subsequent visitors, potentially an XSS vector.
{
"affected": [
{
"package": {
"ecosystem": "Packagist",
"name": "concrete5/concrete5"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "8.1.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2017-7725"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2023-07-25T22:28:42Z",
"nvd_published_at": "2017-04-13T17:59:00Z",
"severity": "MODERATE"
},
"details": "concrete5 8.1.0 places incorrect trust in the HTTP Host header during caching, if the administrator did not define a \"canonical\" URL on installation of concrete5 using the \"Advanced Options\" settings. Remote attackers can make a GET request with any domain name in the Host header. This is stored and allows for arbitrary domains to be set for certain links displayed to subsequent visitors, potentially an XSS vector.",
"id": "GHSA-2mvg-c6mg-3q63",
"modified": "2023-10-10T14:41:51Z",
"published": "2022-05-13T01:08:38Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-7725"
},
{
"type": "WEB",
"url": "https://hackerone.com/reports/148300"
},
{
"type": "WEB",
"url": "https://packetstormsecurity.com/files/142145/concrete5-8.1.0-Host-Header-Injection.html"
},
{
"type": "WEB",
"url": "https://web.archive.org/web/20210124030008/https://www.securityfocus.com/bid/97649"
},
{
"type": "WEB",
"url": "https://www.exploit-db.com/exploits/41885"
},
{
"type": "WEB",
"url": "http://hyp3rlinx.altervista.org/advisories/CONCRETE5-v8.1.0-HOST-HEADER-INJECTION.txt"
}
],
"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": "Concrete CMS vulnerable to cross-site scripting (XSS)"
}
GHSA-2MVH-4GCP-V67P
Vulnerability from github – Published: 2022-05-01 07:21 – Updated: 2022-05-01 07:21Cross-site scripting (XSS) vulnerability in emfadmin/statusView.do in Tumbleweed EMF Administration Module 6.2.2 Build 4123, and possibly other versions before 6.3.2, allows remote attackers to inject arbitrary web script or HTML via the (1) lineId and (2) sort parameters.
{
"affected": [],
"aliases": [
"CVE-2006-4727"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2006-12-31T05:00:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in emfadmin/statusView.do in Tumbleweed EMF Administration Module 6.2.2 Build 4123, and possibly other versions before 6.3.2, allows remote attackers to inject arbitrary web script or HTML via the (1) lineId and (2) sort parameters.",
"id": "GHSA-2mvh-4gcp-v67p",
"modified": "2022-05-01T07:21:21Z",
"published": "2022-05-01T07:21:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2006-4727"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/42392"
},
{
"type": "WEB",
"url": "http://osvdb.org/ref/28/28722-tumbleweed-emf.txt"
},
{
"type": "WEB",
"url": "http://www.osvdb.org/28722"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-2MVM-8HQH-6R9M
Vulnerability from github – Published: 2023-06-19 12:30 – Updated: 2024-04-04 04:56The AI ChatBot WordPress plugin before 4.5.5 does not sanitize and escape its settings, allowing high-privilege users such as admin to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.
{
"affected": [],
"aliases": [
"CVE-2023-2742"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-06-19T11:15:10Z",
"severity": "MODERATE"
},
"details": "The AI ChatBot WordPress plugin before 4.5.5 does not sanitize and escape its settings, allowing high-privilege users such as admin to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.",
"id": "GHSA-2mvm-8hqh-6r9m",
"modified": "2024-04-04T04:56:49Z",
"published": "2023-06-19T12:30:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-2742"
},
{
"type": "WEB",
"url": "https://wpscan.com/vulnerability/f689442a-a851-4140-a10c-ac579f9da142"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2MVW-CMVF-9WP4
Vulnerability from github – Published: 2024-11-07 06:30 – Updated: 2024-11-07 18:31The WP Booking Calendar WordPress plugin before 10.6.3 does not sanitise and escape some of its Widgets settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
{
"affected": [],
"aliases": [
"CVE-2024-10027"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-11-07T06:15:13Z",
"severity": "MODERATE"
},
"details": "The WP Booking Calendar WordPress plugin before 10.6.3 does not sanitise and escape some of its Widgets settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).",
"id": "GHSA-2mvw-cmvf-9wp4",
"modified": "2024-11-07T18:31:23Z",
"published": "2024-11-07T06:30:34Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-10027"
},
{
"type": "WEB",
"url": "https://wpscan.com/vulnerability/a94c7b64-720a-47f1-a74a-691c3a9ed3a1"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2MVW-XXR6-2F56
Vulnerability from github – Published: 2025-06-06 15:30 – Updated: 2026-04-01 18:35Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in M A Vinoth Kumar Frontend Dashboard allows Stored XSS. This issue affects Frontend Dashboard: from n/a through 2.2.8.
{
"affected": [],
"aliases": [
"CVE-2025-49310"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-06-06T13:15:46Z",
"severity": "MODERATE"
},
"details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in M A Vinoth Kumar Frontend Dashboard allows Stored XSS. This issue affects Frontend Dashboard: from n/a through 2.2.8.",
"id": "GHSA-2mvw-xxr6-2f56",
"modified": "2026-04-01T18:35:22Z",
"published": "2025-06-06T15:30:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-49310"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/wordpress/plugin/frontend-dashboard/vulnerability/wordpress-frontend-dashboard-2-2-8-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"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:L",
"type": "CVSS_V3"
}
]
}
GHSA-2MW3-CGXQ-9PRQ
Vulnerability from github – Published: 2026-04-08 09:31 – Updated: 2026-04-10 18:31Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Ronald Huereca Custom Query Blocks post-type-archive-mapping allows DOM-Based XSS.This issue affects Custom Query Blocks: from n/a through <= 5.5.0.
{
"affected": [],
"aliases": [
"CVE-2026-39575"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-08T09:16:28Z",
"severity": "MODERATE"
},
"details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in Ronald Huereca Custom Query Blocks post-type-archive-mapping allows DOM-Based XSS.This issue affects Custom Query Blocks: from n/a through \u003c= 5.5.0.",
"id": "GHSA-2mw3-cgxq-9prq",
"modified": "2026-04-10T18:31:16Z",
"published": "2026-04-08T09:31:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-39575"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/Wordpress/Plugin/post-type-archive-mapping/vulnerability/wordpress-custom-query-blocks-plugin-5-5-0-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"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:L",
"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.