CVE-2021-23980

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2023-02-16 · updated 2026-06-17
Weakness: CWE-79

Description

A mutation XSS affects users calling bleach.clean with all of: svg or math in the allowed tags p or br in allowed tags style, title, noscript, script, textarea, noframes, iframe, or xmp in allowed tags the keyword argument strip_comments=False Note: none of the above tags are in the default allowed tags and strip_comments defaults to True.

Affected products

Mozilla Bleach: before 3.3.0 — fixed in 3.3.0

How to fix

Upgrade to a fixed version: Mozilla Bleach 3.3.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=CVE-2021-23980
https://github.com/mozilla/bleach/security/advisories/GHSA-vv2x-vrpj-qqpq
https://bugzilla.mozilla.org/show_bug.cgi?id=CVE-2021-23980
https://github.com/mozilla/bleach/security/advisories/GHSA-vv2x-vrpj-qqpq

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