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VulnerabilityPublished

CVE-2026-54889: leandrocp mdex · Cross-site Scripting

Affects leandrocp mdexSource CVE Database V5

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Not known to be exploited · CVSS 5.1 Medium : upgrade to 0.13.2 when convenient.

Data as of 10 Nov 2026, 23:24 UTC

CVSS 4.0 base score
5.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.13.2, 2817147f5b87ce7186aa604c9ee72499485b8f2f
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

What to do

Upgrade mdex to 0.13.2; mdex to 2817147f5b87ce7186aa604c9ee72499485b8f2f.

Affected software

ProductAffectedFixed in
leandrocpmdexAffected
  • >=0.8.3 <0.13.2
Fixed in
  • 0.13.2
leandrocpmdexAffected
  • ≥ 9852db2456fdc9d856eb636603a7f608e22e3793, < 2817147f5b87ce7186aa604c9ee72499485b8f2f
Fixed in
  • 2817147f5b87ce7186aa604c9ee72499485b8f2f
Hexmdexpkg:hex/mdexOther threatsAffected
  • >=0.8.3 <0.13.2
Fixed in
  • 0.13.2

CPE configurations (1)

  • cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid rendering untrusted Markdown content with mdex or ensure that URLs in Markdown are sanitized and validated to disallow javascript: schemes before conversion to Quill Delta.

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. '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.

References

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