CheckUser Extension up to 1.39.12/1.42.6/1.43.1 on Mediawiki Special:CheckUser Interface cross site scripting

Summaryinfo

A vulnerability was found in CheckUser Extension up to 1.39.12/1.42.6/1.43.1 on Mediawiki. It has been declared as problematic. Affected by this issue is some unknown functionality of the component Special:CheckUser Interface. Executing a manipulation can lead to cross site scripting. This vulnerability is registered as CVE-2025-53479. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability has been found in CheckUser Extension up to 1.39.12/1.42.6/1.43.1 on Mediawiki and classified as problematic. This vulnerability affects some unknown processing of the component Special:CheckUser Interface. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

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 1.39.X before 1.39.13, from 1.42.X before 1.42.7, from 1.43.X before 1.43.2.

The advisory is shared for download at phabricator.wikimedia.org. This vulnerability was named CVE-2025-53479 since 06/30/2025. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 1.39.13, 1.42.7 or 1.43.2 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-20666). Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• CheckUser Extension

Version

• 1.39.0
• 1.39.1
• 1.39.2
• 1.39.3
• 1.39.4
• 1.39.5
• 1.39.6
• 1.39.7
• 1.39.8
• 1.39.9
• 1.39.10
• 1.39.11
• 1.39.12
• 1.42.0
• 1.42.1
• 1.42.2
• 1.42.3
• 1.42.4
• 1.42.5
• 1.42.6
• 1.43.0
• 1.43.1

CPE 2.3info

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CPE 2.2info

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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