CVE-2026-54889
Severity CVSS v4.0:
MEDIUM
Type:
CWE-79
Cross-Site Scripting (XSS)
Publication date:
29/06/2026
Last modified:
30/06/2026
Description
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.<br />
<br />
&#39;Elixir.MDEx&#39;:to_delta/2 converts Markdown into a Quill Delta. &#39;Elixir.MDEx.DeltaConverter&#39;: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.<br />
<br />
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 or , 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 generally does not execute in modern browsers.<br />
<br />
This issue affects mdex: from 0.8.3 before 0.13.2.
Impact
Base Score 4.0
5.10
Severity 4.0
MEDIUM
References to Advisories, Solutions, and Tools
- https://cna.erlef.org/cves/CVE-2026-54889.html
- https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f
- https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph
- https://osv.dev/vulnerability/EEF-CVE-2026-54889
- https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph