Reflected XSS Vulnerability in Mediawiki's CheckUser Extension

CVE-2025-53479

What is CVE-2025-53479?

The CheckUser extension for Mediawiki is susceptible to reflected Cross-Site Scripting (XSS) attacks through a vulnerability in the Special:CheckUser interface. Specifically, the rev-deleted-user message is displayed without adequate escaping, allowing attackers to inject malicious JavaScript code using the uselang=x-xss language override mechanism. This presents a significant risk to users' data and could lead to unauthorized information disclosure if exploited. It is crucial for administrators to promptly upgrade to the latest version to mitigate this risk.

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