CVE-2025-67478: Mediawiki Checkuser

High severity, CVSS 8.8. EPSS: 0.4% chance of exploitation in the next 30 days.

Vulnerability in Wikimedia Foundation CheckUser. This vulnerability is associated with program files includes/Mail/UserMailer.Php. This issue affects CheckUser: from * before 1.39.14, 1.43.4, 1.44.1.

Affected products

• Mediawiki Checkuser: from 1.39.0, before 1.39.14 (fixed in 1.39.14); from 1.43.0, before 1.43.4 (fixed in 1.43.4); version 1.44.0 only

Published 2026-02-03. Last modified 2026-06-17.