CVE-2025-53479 CheckUser: Reflected Cross-Site Scripting (XSS) in Special:CheckUser via unsanitized internationalized message
Attackers can execute arbitrary JavaScript in victims' browsers via reflected XSS in the CheckUser interface, potentially leading to session hijacking.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2025-53479?
CVE-2025-53479 is a medium-severity cross-site scripting vulnerability in Wikimedia Foundation Mediawiki - CheckUser extension, published on 8 Jul 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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 1.42.X before 1.42.7, from 1.43.X before 1.43.2.
Weakness: CWE-79
Which versions are affected by CVE-2025-53479?
How do I fix CVE-2025-53479?
No fix has been published for CVE-2025-53479 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2025-53479 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-53479 exists.
Sources
Also known as GHSA-mjwg-jq5c-p8xr.