CVE-2021-38497: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Through use of reportValidity() and window.open(), a plain-text validation message could have been overlaid on another origin, leading to possible user confusion and spoofing attacks. This vulnerability affects Firefox < 93, Thunderbird < 91.2, and Firefox ESR < 91.2.

Affected products

• Mozilla Firefox: before 93.0 (fixed in 93.0)
• Mozilla Firefox ESR: before 91.2 (fixed in 91.2)
• Mozilla Thunderbird: before 91.2 (fixed in 91.2)

Published 2021-11-03. Last modified 2026-06-17.