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.\n\nThis issue affects mdex: from 0.8.3 before 0.13.2.","state":"PUBLISHED","assigner":"EEF","published_at":"2026-06-29 20:17:39","updated_at":"2026-06-30 14:14:35"},"problem_types":["CWE-79","CWE-79 CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')"],"metrics":[{"version":"4.0","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","type":"Secondary","score":"5.1","severity":"MEDIUM","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/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","data":{"version":"4.0","vectorString":"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/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","baseScore":5.1,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}},{"version":"4.0","source":"CNA","type":"CVSS","score":"5.1","severity":"MEDIUM","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","data":{"attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":5.1,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"LOW","userInteraction":"ACTIVE","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"LOW"}}],"references":[{"url":"https://cna.erlef.org/cves/CVE-2026-54889.html","name":"https://cna.erlef.org/cves/CVE-2026-54889.html","refsource":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f","name":"https://github.com/leandrocp/mdex/commit/2817147f5b87ce7186aa604c9ee72499485b8f2f","refsource":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph","name":"https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph","refsource":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-54889","name":"https://osv.dev/vulnerability/EEF-CVE-2026-54889","refsource":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-54889","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54889","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"leandrocp","product":"mdex","version":"affected 0.8.3 0.13.2 semver","platforms":[]},{"source":"CNA","vendor":"leandrocp","product":"mdex","version":"affected 9852db2456fdc9d856eb636603a7f608e22e3793 2817147f5b87ce7186aa604c9ee72499485b8f2f git","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[{"source":"CNA","title":"","value":"Sanitize the Quill Delta produced by 'Elixir.MDEx':to_delta/2 before rendering it: drop or blank any \"link\" or \"image\" value whose URL scheme is not in a safe allowlist (http, https, mailto, tel).","time":"","lang":"en"}],"exploits":[],"credits":[{"source":"CNA","value":"Peter Ullrich","lang":"en"},{"source":"CNA","value":"Leandro Pereira","lang":"en"},{"source":"CNA","value":"Jonatan Männchen / EEF","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"54889","cve":"CVE-2026-54889","epss":"0.003100000","percentile":"0.226340000","score_date":"2026-06-30","updated_at":"2026-07-01 00:05:16"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-54889","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-06-29T20:48:34.044130Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-06-29T20:48:52.206Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"references":[{"tags":["exploit"],"url":"https://github.com/leandrocp/mdex/security/advisories/GHSA-4383-7xfp-gpph"}],"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"],"defaultStatus":"unaffected","modules":["'Elixir.MDEx'","'Elixir.MDEx.DeltaConverter'"],"packageName":"mdex","packageURL":"pkg:hex/mdex","product":"mdex","programFiles":["lib/mdex.ex","lib/mdex/delta_converter.ex"],"programRoutines":[{"name":"'Elixir.MDEx':to_delta/2"},{"name":"'Elixir.MDEx.DeltaConverter':convert/2"},{"name":"'Elixir.MDEx.DeltaConverter':default_convert_node/3"}],"repo":"https://github.com/leandrocp/mdex","vendor":"leandrocp","versions":[{"lessThan":"0.13.2","status":"affected","version":"0.8.3","versionType":"semver"}]},{"collectionURL":"https://github.com","cpes":["cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*"],"defaultStatus":"unaffected","modules":["'Elixir.MDEx'","'Elixir.MDEx.DeltaConverter'"],"packageName":"leandrocp/mdex","packageURL":"pkg:github/leandrocp/mdex","product":"mdex","programFiles":["lib/mdex.ex","lib/mdex/delta_converter.ex"],"programRoutines":[{"name":"'Elixir.MDEx':to_delta/2"},{"name":"'Elixir.MDEx.DeltaConverter':convert/2"},{"name":"'Elixir.MDEx.DeltaConverter':default_convert_node/3"}],"repo":"https://github.com/leandrocp/mdex","vendor":"leandrocp","versions":[{"lessThan":"2817147f5b87ce7186aa604c9ee72499485b8f2f","status":"affected","version":"9852db2456fdc9d856eb636603a7f608e22e3793","versionType":"git"}]}],"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"The application must pass untrusted Markdown to 'Elixir.MDEx':to_delta/2 and then render the resulting Quill Delta to HTML with a renderer that maps the \"link\" and \"image\" attributes to href and src without applying its own URL scheme sanitization (for example quill-delta-to-html or the Quill client).
"}],"value":"The application must pass untrusted Markdown to 'Elixir.MDEx':to_delta/2 and then render the resulting Quill Delta to HTML with a renderer that maps the \"link\" and \"image\" attributes to href and src without applying its own URL scheme sanitization (for example quill-delta-to-html or the Quill client)."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:leandrocp:mdex:*:*:*:*:*:*:*:*","versionEndExcluding":"0.13.2","versionStartIncluding":"0.8.3","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Peter Ullrich"},{"lang":"en","type":"remediation developer","value":"Leandro Pereira"},{"lang":"en","type":"analyst","value":"Jonatan Männchen / EEF"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"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.
"}],"value":"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