{"cve":"CVE-2026-54889","nvd":{"published":"2026-06-29T20:17:39.407","modified":"2026-10-25T21:10:00.770","status":"Deferred","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.\n\n'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.\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 <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.\n\nThis issue affects mdex: from 0.8.3 before 0.13.2.","cvss_v4":{"vector":"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","score":5.1},"cvss_v3":null,"cwes":["CWE-79"],"references":["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"],"products":[],"source":"nvd","synced_at":"2026-10-25T23:44:33.281319194+00:00"},"epss":{"cve":"CVE-2026-54889","score":0.00538,"percentile":0.45047,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}