CVE-2025-53479

CheckUser: Reflected Cross-Site Scripting (XSS) in Special:CheckUser via unsanitized internationalized message

MEDIUM
5.4
CVSS Score
Published: July 8, 2025 at 05:16 PM UTC
Updated: June 17, 2026 at 09:38 AM UTC
1 product affected across 1 vendorCheckUser

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.2%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

1.42.x ≤ v < 1.42.71.43.x ≤ v < 1.43.21.42.x1.43.x
Affected range stops below 1.42.7, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.43.2, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (2)

Source: c4f26cc8-17ff-4c99-b5e2-38fc1793eacc
https://phabricator.wikimedia.org/T394693

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79

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