CVE-2026-34090: Mediawiki Checkuser

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Wikimedia Foundation CheckUser. This issue affects CheckUser: from 1.45.0 before 1.45.2.

Affected products

• Mediawiki Checkuser: from 1.45.0, before 1.45.2 (fixed in 1.45.2)

Published 2026-05-11. Last modified 2026-06-17.