XSS in Starcitizenwiki Mediawiki-Extensions-Embedvideo
CVE-2026-55691
The EmbedVideo Extension is a MediaWiki extension which adds a parser function called #ev and various parser tags for embedding video clips from various video sharing services. Prior to 4.1.0, EmbedHtmlFormatter::toHtml in includes/EmbedService/EmbedHtmlFormatter.php passes the user-supplied class value directly to sprintf while constructing a figure element. A quote in the class value can terminate the class attribute and inject arbitrary HTML attributes or markup into the rendered page. A user able to edit a wiki page can store JavaScript that executes for visitors who render the affected content. This issue is fixed in version 4.1.0.
Vulnerability class: XSS (Cross-Site Scripting)
CVSS v3 metric
CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L.
Affected products
- Starcitizenwiki Mediawiki-extensions-embedvideo — versions < 4.1.0
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-55691?
- CVE-2026-55691 is a high-severity vulnerability in Starcitizenwiki Mediawiki-Extensions-Embedvideo, classified under Cross-site Scripting. CVSS score: 8.6/10. Published 2026-09-15.
- How severe is CVE-2026-55691?
- High severity. CVSS v3 base score is 8.6 out of 10.