CVE-2021-23972: Mozilla Firefox

High severity, CVSS 8.8. EPSS: 1% chance of exploitation in the next 30 days.

One phishing tactic on the web is to provide a link with HTTP Auth. For example 'https://www.phishingtarget.com@evil.com'. To mitigate this type of attack, Firefox will display a warning dialog; however, this warning dialog would not have been displayed if evil.com used a redirect that was cached by the browser. 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.