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

Summaryinfo

A vulnerability described as problematic has been identified in CheckUser Extension up to 1.39.12/1.42.6/1.43.1 on Mediawiki. Affected by this issue is some unknown functionality of the component Special:Investigate Page. Such manipulation leads to cross site scripting. This vulnerability is traded as CVE-2025-53480. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in CheckUser Extension up to 1.39.12/1.42.6/1.43.1 on Mediawiki. It has been rated as problematic. Affected by this issue is an unknown code block of the component Special:Investigate Page. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to 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. Impacted is integrity. CVE summarizes:

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.

The advisory is shared for download at phabricator.wikimedia.org. This vulnerability is handled as CVE-2025-53480 since 06/30/2025. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for 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-2025-20516). 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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Once again VulDB remains the best source for vulnerability data.

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