A race condition could have allowed bypassing the fullscreen notification which could have lead to a fullscreen window spoof being unnoticed.<br>*This bug only affects Firefox for Windows. Other operating systems are unaffected.*. This vulnerability affects Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5.
https://www.mozilla.org/security/advisories/mfsa2022-03/
https://www.mozilla.org/security/advisories/mfsa2022-02/