CVE-2021-23974: Mozilla Firefox

Medium severity, CVSS 6.1. EPSS: 0.8% chance of exploitation in the next 30 days.

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)

Published 2021-02-26. Last modified 2026-06-17.