CVE-2026-39936Public exploitNetwork attack vector

Stored XSS via unreserved link data attributes

Published Apr 7, 2026 · Updated Apr 7, 2026

Stored XSS in Wikimedia Foundation Score before MediaWiki 1.43 allows remote attackers to run script through crafted data attributes. The popup code reads attacker-controlled data-midi and data-source values from an enclosing mw-ext-score element and assigns them directly to link href attributes without scheme sanitization. Exploitation requires control of custom HTML plus an inserted image element, such as a Scribunto-generated SVG, and a reader must click the image and then a popup link; the script executes with that reader's site privileges.

CVSS severity6.9
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Wikimedia Foundation Score before MediaWiki 1.43 allows remote attackers to run script through crafted data attributes. The popup code reads attacker-controlled data-midi and data-source values from an enclosing mw-ext-score element and assigns them directly to link href attributes without scheme sanitization. Exploitation requires control of custom HTML plus an inserted image element, such as a Scribunto-generated SVG, and a reader must click the image and then a popup link; the script executes with that reader's site privileges.

The record

CVE
CVE-2026-39936
Published
Apr 7, 2026
Updated
Apr 7, 2026
Vendor
Wikimedia Foundation
Product
Score
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 versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Wikimedia Foundation · ScoreAffected 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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

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

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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