CVE-2026-54889 (GCVE-0-2026-54889)
Vulnerability from cvelistv5 – Published: 2026-06-29 19:10 – Updated: 2026-06-30 04:38
VLAI
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 (v2.0.3)
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
Credits
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"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-54889\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-29T20:48:34.044130Z\"}}}], \"references\": [{\"url\": \"https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-29T20:48:47.453Z\"}}], \"cna\": {\"title\": \"Unsanitized URL schemes in MDEx Quill Delta output allow javascript: injection (XSS)\", \"source\": {\"discovery\": \"EXTERNAL\"}, \"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\"}], \"impacts\": [{\"capecId\": \"CAPEC-244\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-244 XSS Targeting URI Placeholders\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"version\": \"4.0\", \"baseScore\": 5.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"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\", \"userInteraction\": \"ACTIVE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"LOW\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"LOW\", \"vulnConfidentialityImpact\": \"LOW\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/leandrocp/mdex\", \"vendor\": \"leandrocp\", \"modules\": [\"\u0027Elixir.MDEx\u0027\", \"\u0027Elixir.MDEx.DeltaConverter\u0027\"], \"product\": \"mdex\", \"versions\": [{\"status\": \"affected\", \"version\": \"0.8.3\", \"lessThan\": \"0.13.2\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:hex/mdex\", \"packageName\": \"mdex\", \"programFiles\": [\"lib/mdex.ex\", \"lib/mdex/delta_converter.ex\"], \"collectionURL\": \"https://repo.hex.pm\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.MDEx\u0027:to_delta/2\"}, {\"name\": \"\u0027Elixir.MDEx.DeltaConverter\u0027:convert/2\"}, {\"name\": \"\u0027Elixir.MDEx.DeltaConverter\u0027:default_convert_node/3\"}]}, {\"cpes\": [\"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/leandrocp/mdex\", \"vendor\": \"leandrocp\", \"modules\": [\"\u0027Elixir.MDEx\u0027\", \"\u0027Elixir.MDEx.DeltaConverter\u0027\"], \"product\": \"mdex\", \"versions\": [{\"status\": \"affected\", \"version\": \"9852db2456fdc9d856eb636603a7f608e22e3793\", \"lessThan\": \"2817147f5b87ce7186aa604c9ee72499485b8f2f\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/leandrocp/mdex\", \"packageName\": \"leandrocp/mdex\", \"programFiles\": [\"lib/mdex.ex\", \"lib/mdex/delta_converter.ex\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.MDEx\u0027:to_delta/2\"}, {\"name\": \"\u0027Elixir.MDEx.DeltaConverter\u0027:convert/2\"}, {\"name\": \"\u0027Elixir.MDEx.DeltaConverter\u0027:default_convert_node/3\"}]}], \"references\": [{\"url\": \"https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-54889.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-54889\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"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).\", \"supportingMedia\": [{\"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\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-79\", \"description\": \"CWE-79 Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}], \"configurations\": [{\"lang\": \"en\", \"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).\", \"supportingMedia\": [{\"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\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"0.13.2\", \"versionStartIncluding\": \"0.8.3\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-06-30T04:38:42.158Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-54889\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-30T04:38:42.158Z\", \"dateReserved\": \"2026-06-16T10:47:13.915Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-06-29T19:10:49.841Z\", \"assignerShortName\": \"EEF\"}",
"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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