Zitat von MITs Forum am 2. Juni 2023, 0:00 Uhr

A lack of in app notification for entering fullscreen mode could have lead to a malicious website spoofing browser chrome.
*This bug only affects Firefox Focus. Other versions of Firefox are unaffected.*. This vulnerability affects Firefox < 110 and Firefox ESR < 102.8.

References
https://bugzilla.mozilla.org/show_bug.cgi?id=1800203
https://www.mozilla.org/security/advisories/mfsa2023-05/
https://www.mozilla.org/security/advisories/mfsa2023-06/