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CVE-2025-53480: CheckUser: Reflected Cross-Site Scripting (XSS) in Special:Investigate (Account information tab) via unsanitized i18n messages
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.
Classification
CVE ID: CVE-2025-53480
Problem Types
CWE-79 Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting')Affected Products
Vendor: Wikimedia Foundation
Product: Mediawiki - CheckUser extension
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.03% (probability of being exploited)
EPSS Percentile: 6.37% (scored less or equal to compared to others)
EPSS Date: 2025-07-11 (when was this score calculated)
References
https://nvd.nist.gov/vuln/detail/CVE-2025-53480https://phabricator.wikimedia.org/T394700
https://gerrit.wikimedia.org/r/q/I777fc55fef15c3b00df0db268af2b64cb2d6e381