The z-order of the browser windows could be manipulated to hide the fullscreen notification. This could potentially be leveraged to perform a spoofing attack. This vulnerability affects Firefox < 135 and Thunderbird < 135.
{ "availability": "No subscription required", "binaries": [ { "binary_version": "135.0+build2-0ubuntu0.20.04.1", "binary_name": "firefox" }, { "binary_version": "135.0+build2-0ubuntu0.20.04.1", "binary_name": "firefox-dev" }, { "binary_version": "135.0+build2-0ubuntu0.20.04.1", "binary_name": "firefox-geckodriver" }, { "binary_version": "135.0+build2-0ubuntu0.20.04.1", "binary_name": "firefox-mozsymbols" } ] }