Vulnerability · Published Apr 7, 2026 · Assigned by wikimedia-foundation

CVE-2026-39838ProofreadPage improperly sanitizes multiline styles using Sanitizer::checkCSS

Medium 6.9

In plain English

A medium-severity cross-site scripting in MediaWiki - ProofreadPage Extension from Wikimedia Foundation. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 32% of all known vulnerabilities).

Severity (CVSS 4.0)6.9Medium

Exploit odds (30 days)0.4%top 67.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Improper neutralization of input during web page generation ('cross-site scripting') vulnerability in Wikimedia Foundation MediaWiki - ProofreadPage Extension allows XSS Targeting Non-Script Elements. The issue has been remediated on the `master` branch, and in the release branches for MediaWiki versions 1.43, 1.44, and 1.45.

Affected products (as reported)

Vendor	Product	Versions
Wikimedia Foundation	MediaWiki - ProofreadPage Extension	0 – before 1.43

Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:N/SA:N

In plain English

Official description

Affected products (as reported)

References