{"id":"CVE-2026-55691","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-55691","summary":"StarCitizenWiki Extension Embed Video: Stored XSS via unsanitized class passed to template","details":"### Summary\nThe user supplied class value is fed directly into the sprintf call that creates HTML. You can add a quote to escape the class and then inject arbitrary html/javascript to the final output.\n\n### Details\nThe template [here](https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/a573a16d925ee0ea0d34b360856dc8ab0b88f822/includes/EmbedService/EmbedHtmlFormatter.php#L138) adds a figure with a class that is substituted in. This value is provided to sprintf [here](https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/a573a16d925ee0ea0d34b360856dc8ab0b88f822/includes/EmbedService/EmbedHtmlFormatter.php#L156), an unescaped version of the class supplied by the user.\n\n```\n$template = <<<HTML\n    <figure class=\"%s\" data-service=\"%s\" %s %s>\n        <div class=\"embedvideo-wrapper\" %s>%s%s%s</div>%s\n    </figure>\nHTML;\n```\n\n### PoC\nNote the double quote immediately following the single quote to escape the class attribute in the template:\n```\n<youtube class='\" onmouseover=\"alert(document.domain)' id=\"dQw4w9WgXcQ\">dQw4w9WgXcQ</youtube>\n```\n\n### Impact\nArbitrary HTML can be inserted into the DOM by any user on any page, allowing for JavaScript to be executed.","published":"2026-06-19T21:15:03Z","modified":"2026-09-10T03:50:48.730623590Z","cvss":{"score":8.6,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Packagist","name":"starcitizenwiki/embedvideo","fixedVersion":"4.1.0"}],"fix":{"url":"https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/commit/370156335b325bb81d14d89edf0a1f2643d50a84","label":"StarCitizenWiki/mediawiki-extensions-EmbedVideo@3701563"},"references":[{"type":"WEB","url":"https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/security/advisories/GHSA-7h5p-637f-jfr7"},{"type":"WEB","url":"https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/commit/370156335b325bb81d14d89edf0a1f2643d50a84"},{"type":"PACKAGE","url":"https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo"},{"type":"WEB","url":"https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/releases/tag/v4.1.0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-10T03:50:48.730623590Z"}}