Medium severity · published Apr 7, 2026
CVE-2026-39838
ProofreadPage improperly sanitizes multiline styles using Sanitizer::checkCSS
6.9
CVSS
0.4%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 34% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MP
MediaWiki - ProofreadPage Extension · Wikimedia Foundation
before 1.43 · source: vendor
Affected product
MP
MediaWiki - ProofreadPage Extension
Wikimedia Foundation
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39838
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39838
gerrit.wikimedia.org
https://gerrit.wikimedia.org/r/q/Idd51e18479b32b7176b43ff74ca1c49d6bdd0628
phabricator.wikimedia.org
https://phabricator.wikimedia.org/T406088
More from MediaWiki - ProofreadPage Extension
6.1
CVE-2026-0670
Stored XSS through a system message and a user-provided parameter in ProofreadPage