Vulnerability · Published Jul 8, 2025 · Assigned by wikimedia-foundation

CVE-2025-53479CheckUser: Reflected Cross-Site Scripting (XSS) in Special:CheckUser via unsanitized internationalized message

Medium 5.4

In plain English

A medium-severity cross-site scripting in Mediawiki - CheckUser extension from Wikimedia Foundation. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).

Severity (CVSS 3.1)5.4Medium

Exploit odds (30 days)0.2%top 90.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

The CheckUser extension’s Special:CheckUser interface is vulnerable to reflected XSS via the rev-deleted-user message. This message is rendered without proper escaping, making it possible to inject JavaScript through the uselang=x-xss language override mechanism. This issue affects Mediawiki - CheckUser extension: from 1.42.X before 1.42.7, from 1.43.X before 1.43.2.

Affected products (as reported)

Vendor	Product	Versions
Wikimedia Foundation	Mediawiki - CheckUser extension	1.42.x – before 1.42.71.43.x – before 1.43.2

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

In plain English

Official description

Affected products (as reported)

References