CVE-2021-36126: Mediawiki

Critical severity, CVSS 9.8. EPSS: 1.2% chance of exploitation in the next 30 days.

An issue was discovered in the AbuseFilter extension in MediaWiki through 1.36. If the MediaWiki:Abusefilter-blocker message is invalid within the content language, the filter user falls back to the English version, but that English version could also be invalid on a wiki. This would result in a fatal error, and potentially fail to block or restrict a potentially nefarious user.

Affected products

• Mediawiki Mediawiki: up to and including 1.36

Published 2021-07-02. Last modified 2026-06-17.