CVE-2025-61651Network attack vector

XSS via unescaped username HTML insertion

Published Feb 3, 2026 · Updated Feb 3, 2026

Cross-site scripting in Wikimedia Foundation CheckUser before 1.44.1 allows remote authenticated users to execute browser scripts. The buildUserElement helper assigns rendered username content to innerHTML instead of a text node, causing embedded markup to be interpreted. Exploitation requires CheckUser privileges and a crafted internationalization context; injected script runs in the affected page's browser origin.

CVSS severity6.1
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Wikimedia Foundation CheckUser before 1.44.1 allows remote authenticated users to execute browser scripts. The buildUserElement helper assigns rendered username content to innerHTML instead of a text node, causing embedded markup to be interpreted. Exploitation requires CheckUser privileges and a crafted internationalization context; injected script runs in the affected page's browser origin.

The record

CVE
CVE-2025-61651
Published
Feb 3, 2026
Updated
Feb 3, 2026
Vendor
Wikimedia Foundation
Product
CheckUser
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Feb 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=* <1.44.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Wikimedia Foundation · CheckUserversion=* <1.44.1

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
0.0Wikimedia FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N/E:U

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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