CheckUser: Reflected Cross-Site Scripting (XSS) in Special:CheckUser via unsanitized internationalized message
Priority MEDIUM 58CWE-79Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-79.
Summary
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.
Why it matters now
Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00198 9th percentileScored 2026-11-07
Fix Fixed Mediawiki - CheckUser extension (Wikimedia Foundation): 1.42.7, 1.43.2
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Wikimedia Foundation | Mediawiki - CheckUser extension | 1.42.x to before 1.42.7; 1.43.x to before 1.43.2 | 1.42.7, 1.43.2 | Patch available | CNA |
- Mediawiki - CheckUser extension VendorWikimedia Foundation Affected 1.42.x to before 1.42.7; 1.43.x to before 1.43.2 Fixed in 1.42.7, 1.43.2 Patch available CNA
Remediation
- Fix · CNA Mediawiki - CheckUser extension (Wikimedia Foundation) Fixed in 1.42.7, 1.43.2
Timeline
- 2026-10-02 Threatist record created from CVE-2025-53479
- 2026-10-03 Alias added: GHSA-mjwg-jq5c-p8xr
References
More Wikimedia Foundation vulnerabilities
- TI-2025-11006 The compare API module breaks Extension:Lockdown CVSS 4.0CRITICAL 10.0
- TI-2024-32110 Backticks can allow the usage of not-allowed SQL functions CVSS 4.0HIGH 8.8
- TI-2026-65500 Unauthenticated SQL injection in UserPageViewTracker via filterusers and ignoreusers parameters CVSS 3.1HIGH 7.5
- TI-2026-64588 DataTransfer depends on phpspreadsheet version vulnerable to CVE-2026-59933 (XLS/OLE memory exhaustion) CVSS 3.1HIGH 7.5
- TI-2026-42112 SQLi in Cargo extension via year range filter CVSS 4.0MEDIUM 6.9
- TI-2026-42110 Stored XSS through Cargo's map format CVSS 4.0MEDIUM 6.9
Sources
- CVE-2025-53479 · CVE Program
- CVE-2025-53479 · NVD
- FIRST EPSS
- GHSA-mjwg-jq5c-p8xr · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences