What’s Vulnerable › Vulnerabilities

CVE-2025-53480: CheckUser: Reflected Cross-Site Scripting (XSS) in Special:Investigate (Account information tab) via unsanitized i18n messages

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-07-08 · updated 2026-06-17
• Weakness: CWE-79

Description

The CheckUser extension’s Special:Investigate page has a vulnerability in the Account information tab, where specific internationalized messages are rendered without proper escaping. Attackers can exploit this by appending ?uselang=x-xss to the URL, causing reflected XSS when the UI renders affected message keys. This issue affects Mediawiki - CheckUser extension: from 1.39.X before 1.39.13, from 1.42.X before 1.42.7, from 1.43.X before 1.43.2.

Affected products

• Wikimedia Foundation Mediawiki - CheckUser extension: from 1.39.x before 1.39.13; from 1.42.x before 1.42.7; from 1.43.x before 1.43.2 — fixed in 1.39.13, 1.42.7, 1.43.2

How to fix

Upgrade to a fixed version: Wikimedia Foundation Mediawiki - CheckUser extension 1.39.13, 1.42.7, 1.43.2. Check the vendor advisory for mitigations.

References

• https://gerrit.wikimedia.org/r/q/I777fc55fef15c3b00df0db268af2b64cb2d6e381
• https://phabricator.wikimedia.org/T394700

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