What’s Vulnerable › Vulnerabilities

CVE-2020-35479

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% 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. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value. This affects MediaWiki 1.12.0 and later.

Affected products

• Debian Linux: 9.0, 10.0
• Fedoraproject Fedora: 33
• Wikimedia Foundation MediaWiki: from 1.12.0 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.debian.org/debian-lts-announce/2020/12/msg00034.html
• 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://www.debian.org/security/2020/dsa-4816
• https://lists.debian.org/debian-lts-announce/2020/12/msg00034.html
• 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://www.debian.org/security/2020/dsa-4816

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