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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-38497
• https://bugzilla.mozilla.org/show_bug.cgi?id=1726621
• https://www.mozilla.org/security/advisories/mfsa2021-43/
• https://www.mozilla.org/security/advisories/mfsa2021-45/
• https://www.mozilla.org/security/advisories/mfsa2021-47/