CVE-2021-23974

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-02-26 · updated 2026-06-17

Description

The DOMParser API did not properly process '<noscript>' elements for escaping. This could be used as an mXSS vector to bypass an HTML Sanitizer. This vulnerability affects Firefox < 86.

Affected products

Mozilla Firefox: before 86.0 — fixed in 86.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 86.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=1528997%2C1683627
https://security.gentoo.org/glsa/202104-10
https://www.mozilla.org/security/advisories/mfsa2021-07/
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1528997%2C1683627
https://security.gentoo.org/glsa/202104-10
https://www.mozilla.org/security/advisories/mfsa2021-07/

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