PT-2026-53687 · Leandrocp · Mdex

Leandro Pereira + 1 · Published 2026-06-29 · Updated 2026-06-29 · CVE-2026-54889

NVD

CVSS v4.0

5.1

Medium

Base vector

AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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) 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.

This issue affects mdex: from 0.8.3 before 0.13.2.

Exploit

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

CVE-2026-54889

Affected Products

Mdex

References · 5

• 🔥 https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph · Exploit
• https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-54889 · Security Note
• https://osv.dev/vulnerability/EEF-CVE-2026-54889 · Note
• https://cna.erlef.org/cves/CVE-2026-54889.html · Note