CVE-2026-39838
ProofreadPage improperly sanitizes multiline styles using Sanitizer::checkCSS
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.This issue affects .
INFO
Published Date :
April 7, 2026, 8:16 p.m.
Last Modified :
April 7, 2026, 8:16 p.m.
Remotely Exploit :
Yes !
Source :
c4f26cc8-17ff-4c99-b5e2-38fc1793eacc
Affected Products
The following products are affected by CVE-2026-39838
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | c4f26cc8-17ff-4c99-b5e2-38fc1793eacc | ||||
| CVSS 4.0 | MEDIUM | c4f26cc8-17ff-4c99-b5e2-38fc1793eacc |
Solution
- Sanitize all user-provided input before rendering.
- Update the ProofreadPage Extension to the latest version.
- Implement strict output encoding for web content.
- Review and enforce input validation rules.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-39838.
| URL | Resource |
|---|---|
| https://gerrit.wikimedia.org/r/q/Idd51e18479b32b7176b43ff74ca1c49d6bdd0628 | |
| https://phabricator.wikimedia.org/T406088 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-39838 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-39838
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-39838 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-39838 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by c4f26cc8-17ff-4c99-b5e2-38fc1793eacc
Apr. 07, 2026
Action Type Old Value New Value Added 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.This issue affects . Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-79 Added Reference https://gerrit.wikimedia.org/r/q/Idd51e18479b32b7176b43ff74ca1c49d6bdd0628 Added Reference https://phabricator.wikimedia.org/T406088