CVE-2026-55691: Starcitizenwiki Mediawiki-Extensions-Embedvideo

High severity, CVSS 8.6. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Starcitizenwiki Mediawiki-Extensions-Embedvideo: before 4.1.0 (fixed in 4.1.0)

Published 2026-09-15. Last modified 2026-09-30.