CVE-2026-54889: leandrocp mdex · Cross-site Scripting
Affects leandrocp mdexSource CVE Database V5
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
- 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:NExploitation evidence
Disclosed: evidence found.
CVE published 29 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| leandrocpmdex | Affected
| Fixed in
|
| leandrocpmdex | Affected
| Fixed in
|
Hexmdexpkg:hex/mdexOther threats | Affected
| Fixed in
|
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
- github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph (opens in a new tab)
- cna.erlef.org/cves/CVE-2026-54889.html (opens in a new tab)
- osv.dev/vulnerability/EEF-CVE-2026-54889 (opens in a new tab)
- github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f (opens in a new tab)