CVE-2020-35478

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2020-12-18 · updated 2026-06-17
Weakness: CWE-79

Description

MediaWiki before 1.35.1 allows XSS via BlockLogFormatter.php. MediaWiki:blanknamespace potentially can be output as raw HTML with SCRIPT tags via LogFormatter::makePageLink(). This affects MediaWiki 1.33.0 and later.

Affected products

Fedoraproject Fedora: 33
Wikimedia Foundation MediaWiki: from 1.33.0 before 1.35.1 — fixed in 1.35.1

How to fix

Upgrade to a fixed version: Wikimedia Foundation MediaWiki 1.35.1. Check the vendor advisory for mitigations.

References

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/STT5Z4A3BCXVH3WIPICWU2FP4IPIMUPC/
https://lists.wikimedia.org/pipermail/mediawiki-announce/2020-December/000268.html
https://phabricator.wikimedia.org/T268938
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/STT5Z4A3BCXVH3WIPICWU2FP4IPIMUPC/
https://lists.wikimedia.org/pipermail/mediawiki-announce/2020-December/000268.html
https://phabricator.wikimedia.org/T268938

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