CVE-2026-54889 (GCVE-0-2026-54889)
Vulnerability from cvelistv5 – Published: 2026-06-29 19:10 – Updated: 2026-06-30 04:38
VLAI
EPSS
VEX
Title
Unsanitized URL schemes in MDEx Quill Delta output allow javascript: injection (XSS)
Summary
Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in leandrocp mdex allows cross-site scripting via unsanitized URL schemes in Quill Delta output.
'Elixir.MDEx':to_delta/2 converts Markdown into a Quill Delta. 'Elixir.MDEx.DeltaConverter':default_convert_node/3 in lib/mdex/delta_converter.ex copies the URL of a link, wikilink, or image node directly from the parsed Markdown into the Delta "link" or "image" attribute without applying a scheme allowlist or any normalization.
An attacker who controls the Markdown text can supply a javascript: URL (for example [click](javascript:alert(document.cookie))) that survives verbatim into the Delta attribute. When the Delta is rendered to HTML by a downstream renderer (such as quill-delta-to-html or the Quill client), the attribute becomes an <a href> or <img src>, and the javascript: scheme executes in the browser of anyone who views the rendered content. The link and wikilink cases are the strongest vectors because javascript: in an href executes on click; the image case is lower impact because javascript: in <img src> generally does not execute in modern browsers.
This issue affects mdex: from 0.8.3 before 0.13.2.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-29 20:48 UTC
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/leandrocp/mdex/security/adviso… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-54889.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-54889 | related |
| https://github.com/leandrocp/mdex/commit/2817147f… | patch |
Impacted products
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"lib/mdex.ex",
"lib/mdex/delta_converter.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MDEx\u0027:to_delta/2"
},
{
"name": "\u0027Elixir.MDEx.DeltaConverter\u0027:convert/2"
},
{
"name": "\u0027Elixir.MDEx.DeltaConverter\u0027:default_convert_node/3"
}
],
"repo": "https://github.com/leandrocp/mdex",
"vendor": "leandrocp",
"versions": [
{
"lessThan": "0.13.2",
"status": "affected",
"version": "0.8.3",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MDEx\u0027",
"\u0027Elixir.MDEx.DeltaConverter\u0027"
],
"packageName": "leandrocp/mdex",
"packageURL": "pkg:github/leandrocp/mdex",
"product": "mdex",
"programFiles": [
"lib/mdex.ex",
"lib/mdex/delta_converter.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MDEx\u0027:to_delta/2"
},
{
"name": "\u0027Elixir.MDEx.DeltaConverter\u0027:convert/2"
},
{
"name": "\u0027Elixir.MDEx.DeltaConverter\u0027:default_convert_node/3"
}
],
"repo": "https://github.com/leandrocp/mdex",
"vendor": "leandrocp",
"versions": [
{
"lessThan": "2817147f5b87ce7186aa604c9ee72499485b8f2f",
"status": "affected",
"version": "9852db2456fdc9d856eb636603a7f608e22e3793",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eThe application must pass untrusted Markdown to \u003ctt\u003e\u0027Elixir.MDEx\u0027:to_delta/2\u003c/tt\u003e and then render the resulting Quill Delta to HTML with a renderer that maps the \u003ctt\u003e\"link\"\u003c/tt\u003e and \u003ctt\u003e\"image\"\u003c/tt\u003e attributes to \u003ctt\u003ehref\u003c/tt\u003e and \u003ctt\u003esrc\u003c/tt\u003e without applying its own URL scheme sanitization (for example \u003ctt\u003equill-delta-to-html\u003c/tt\u003e or the Quill client).\u003c/p\u003e"
}
],
"value": "The application must pass untrusted Markdown to \u0027Elixir.MDEx\u0027:to_delta/2 and then render the resulting Quill Delta to HTML with a renderer that maps the \"link\" and \"image\" attributes to href and src without applying its own URL scheme sanitization (for example quill-delta-to-html or the Quill client)."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.13.2",
"versionStartIncluding": "0.8.3",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Peter Ullrich"
},
{
"lang": "en",
"type": "remediation developer",
"value": "Leandro Pereira"
},
{
"lang": "en",
"type": "analyst",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in leandrocp mdex allows cross-site scripting via unsanitized URL schemes in Quill Delta output.\u003cp\u003e\u003ctt\u003e\u0027Elixir.MDEx\u0027:to_delta/2\u003c/tt\u003e converts Markdown into a Quill Delta. \u003ctt\u003e\u0027Elixir.MDEx.DeltaConverter\u0027:default_convert_node/3\u003c/tt\u003e in \u003ctt\u003elib/mdex/delta_converter.ex\u003c/tt\u003e copies the URL of a link, wikilink, or image node directly from the parsed Markdown into the Delta \u003ctt\u003e\"link\"\u003c/tt\u003e or \u003ctt\u003e\"image\"\u003c/tt\u003e attribute without applying a scheme allowlist or any normalization.\u003c/p\u003e\u003cp\u003eAn attacker who controls the Markdown text can supply a \u003ctt\u003ejavascript:\u003c/tt\u003e URL (for example \u003ctt\u003e[click](javascript:alert(document.cookie))\u003c/tt\u003e) that survives verbatim into the Delta attribute. When the Delta is rendered to HTML by a downstream renderer (such as \u003ctt\u003equill-delta-to-html\u003c/tt\u003e or the Quill client), the attribute becomes an \u003ctt\u003e\u0026lt;a href\u0026gt;\u003c/tt\u003e or \u003ctt\u003e\u0026lt;img src\u0026gt;\u003c/tt\u003e, and the \u003ctt\u003ejavascript:\u003c/tt\u003e scheme executes in the browser of anyone who views the rendered content. The link and wikilink cases are the strongest vectors because \u003ctt\u003ejavascript:\u003c/tt\u003e in an \u003ctt\u003ehref\u003c/tt\u003e executes on click; the image case is lower impact because \u003ctt\u003ejavascript:\u003c/tt\u003e in \u003ctt\u003e\u0026lt;img src\u0026gt;\u003c/tt\u003e generally does not execute in modern browsers.\u003c/p\u003e\u003cp\u003eThis issue affects mdex: from 0.8.3 before 0.13.2.\u003c/p\u003e"
}
],
"value": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in leandrocp mdex allows cross-site scripting via unsanitized URL schemes in Quill Delta output.\n\n\u0027Elixir.MDEx\u0027:to_delta/2 converts Markdown into a Quill Delta. \u0027Elixir.MDEx.DeltaConverter\u0027:default_convert_node/3 in lib/mdex/delta_converter.ex copies the URL of a link, wikilink, or image node directly from the parsed Markdown into the Delta \"link\" or \"image\" attribute without applying a scheme allowlist or any normalization.\n\nAn attacker who controls the Markdown text can supply a javascript: URL (for example [click](javascript:alert(document.cookie))) that survives verbatim into the Delta attribute. When the Delta is rendered to HTML by a downstream renderer (such as quill-delta-to-html or the Quill client), the attribute becomes an \u003ca href\u003e or \u003cimg src\u003e, and the javascript: scheme executes in the browser of anyone who views the rendered content. The link and wikilink cases are the strongest vectors because javascript: in an href executes on click; the image case is lower impact because javascript: in \u003cimg src\u003e generally does not execute in modern browsers.\n\nThis issue affects mdex: from 0.8.3 before 0.13.2."
}
],
"impacts": [
{
"capecId": "CAPEC-244",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-244 XSS Targeting URI Placeholders"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "NETWORK",
"baseScore": 5.1,
"baseSeverity": "MEDIUM",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "LOW",
"subIntegrityImpact": "LOW",
"userInteraction": "ACTIVE",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-79",
"description": "CWE-79 Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-30T04:38:42.158Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-54889.html"
},
{
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-54889"
},
{
"tags": [
"patch"
],
"url": "https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Unsanitized URL schemes in MDEx Quill Delta output allow javascript: injection (XSS)",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eSanitize the Quill Delta produced by \u003ctt\u003e\u0027Elixir.MDEx\u0027:to_delta/2\u003c/tt\u003e before rendering it: drop or blank any \u003ctt\u003e\"link\"\u003c/tt\u003e or \u003ctt\u003e\"image\"\u003c/tt\u003e value whose URL scheme is not in a safe allowlist (\u003ctt\u003ehttp\u003c/tt\u003e, \u003ctt\u003ehttps\u003c/tt\u003e, \u003ctt\u003emailto\u003c/tt\u003e, \u003ctt\u003etel\u003c/tt\u003e).\u003c/p\u003e"
}
],
"value": "Sanitize the Quill Delta produced by \u0027Elixir.MDEx\u0027:to_delta/2 before rendering it: drop or blank any \"link\" or \"image\" value whose URL scheme is not in a safe allowlist (http, https, mailto, tel)."
}
],
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-54889",
"datePublished": "2026-06-29T19:10:49.841Z",
"dateReserved": "2026-06-16T10:47:13.915Z",
"dateUpdated": "2026-06-30T04:38:42.158Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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