{"affected":[{"package":{"ecosystem":"Hex","name":"html_sanitize_ex","purl":"pkg:hex/html_sanitize_ex"},"ranges":[{"events":[{"introduced":"0.3.1"},{"fixed":"1.5.3"}],"type":"SEMVER"}],"versions":["0.3.1","1.0.0","1.0.1","1.1.0-rc1","1.1.0","1.1.1","1.2.0","1.3.0-rc1","1.3.0-rc2","1.3.0-rc3","1.3.0","1.4.0","1.4.1","1.4.2","1.4.3","1.4.4-rc.0","1.4.4","1.5.0-rc.0","1.5.0","1.5.1","1.5.2"]},{"ranges":[{"events":[{"introduced":"8976d64ea0b77d26093a94a43ec48a3978e8d028"},{"fixed":"bec27fec4de99e40c68c4285a610e09e791a3eaf"}],"repo":"https://github.com/rrrene/html_sanitize_ex","type":"GIT"}]}],"aliases":["GHSA-xmm9-jc22-rcgj","CVE-2026-66843"],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"René Föhring","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"ANALYST"}],"database_specific":{"capec_ids":["CAPEC-175"],"cpe_ids":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-829"]},"details":"## Summary\n\nInclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html\\_sanitize\\_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an <object> element in sanitized HTML. object is the one URI-bearing element in lib/html\\_sanitize\\_ex/scrubber/html5.ex never registered through allow\\_tag\\_with\\_uri\\_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through <object data> in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html\\_sanitize\\_ex: from 0.3.1 before 1.5.3.\n\n## Workaround\n\nSanitize with basic\\_html/1, markdown\\_html/1 or strip\\_tags/1, none of which allow object, or define a custom scrubber that omits it.\n\nA Content-Security-Policy of object-src 'none' blocks an injected <object> from loading, and hosting user uploads on a separate origin removes the escalation path.\n\n## Configuration\n\nOnly HtmlSanitizeEx.html5/1, and custom scrubbers declared with use HtmlSanitizeEx, extend: :html5, allow the object element, and the sanitized output must be rendered to other users.\n\nScript execution in the host origin additionally requires the application to serve attacker-controlled HTML from a same-origin path, such as an uploads directory served as text/html.","id":"EEF-CVE-2026-66843","modified":"2026-08-06T14:48:20.978701Z","published":"2026-08-06T14:48:20.513Z","references":[{"type":"ADVISORY","url":"https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-xmm9-jc22-rcgj"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-66843.html"},{"type":"FIX","url":"https://github.com/rrrene/html_sanitize_ex/commit/bec27fec4de99e40c68c4285a610e09e791a3eaf"},{"type":"PACKAGE","url":"https://hex.pm/packages/html_sanitize_ex"}],"related":[],"schema_version":"1.7.3","severity":[{"score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","type":"CVSS_V4"}],"summary":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied `<object>` elements, allowing untrusted content embedding","upstream":[]}