MediaWiki CheckUser 1.39.3: Hidden Usernames Leak (CVE-2023-37252)
CVE-2023-37252 Published on September 14, 2026
An issue was discovered in the CheckUser extension for MediaWiki through 1.39.3. Special:CheckUserLog shows usernames that have been hidden.
Vulnerability Analysis
CVE-2023-37252 is exploitable with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. Public availability of a proof of concept (POC) exploit exists for CVE-2023-37252. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Weakness Type
Incorrect Resource Transfer Between Spheres
The product does not properly transfer a resource/behavior to another sphere, or improperly imports a resource/behavior from another sphere, in a manner that provides unintended control over that resource.
Products Associated with CVE-2023-37252
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Affected Versions
MediaWiki CheckUser:- Before 1.35.11 is affected.
- Version 1.36.0 and below 1.38.7 is affected.
- Version 1.39.0 and below 1.39.4 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.