User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20171112125346 Steps to reproduce: On macOS, click the fullscreen button to go fullscreen, and move mouse to the upper border of screen. Actual results: The menu bar and window decoration appear, covering the tabbar and part of the toolbar. Please see attached file. When I want to switch tab, since the tabbar is at the top, I often accidently move the mouse cursor to the top of the screen, triggering the menubar, and there’s no way to switch tab in that state. It is extremely annoying. Expected results: The menu bar should push the tabbar and the toolbar downward instead of covering them. The traffic light button should appear at the left side of the tabbar (like in non-fullscreen mode). Again, please see attached file.

Confirmed on latest nightly and latest MacOS 13.1