CVE-2023-4053: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.8% chance of exploitation in the next 30 days.

A website could have obscured the full screen notification by using a URL with a scheme handled by an external program, such as a mailto URL. This could have led to user confusion and possible spoofing attacks. This vulnerability affects Firefox < 116, Firefox ESR < 115.2, and Thunderbird < 115.2.

Affected products

• Mozilla Firefox: before 116.0 (fixed in 116.0)

Published 2023-08-01. Last modified 2026-06-17.