CVE-2026-39933Network attack vector

Script execution via unescaped watchlist rendering

Published Apr 7, 2026 · Updated Apr 7, 2026

Cross-site scripting in Wikimedia Foundation MediaWiki GlobalWatchlist Extension before 1.43 allows remote attackers to execute script. Multiple Special:GlobalWatchlist rendering paths concatenate an unescaped site URL or username and render messages or tag descriptions as raw HTML. Exploitation requires attacker-controlled watchlist content to reach one of these paths; injected script runs with the affected wiki viewer's session privileges.

CVSS severity6.9
Medium
EPSS probability0.34%
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 MediaWiki GlobalWatchlist Extension before 1.43 allows remote attackers to execute script. Multiple Special:GlobalWatchlist rendering paths concatenate an unescaped site URL or username and render messages or tag descriptions as raw HTML. Exploitation requires attacker-controlled watchlist content to reach one of these paths; injected script runs with the affected wiki viewer's session privileges.

The record

CVE
CVE-2026-39933
Published
Apr 7, 2026
Updated
Apr 7, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, CAPEC-63, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 7, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.9Wikimedia FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L

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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CAPEC-63Cross-Site Scripting (XSS)
T1203Exploitation for Client Execution

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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