Whenever Firefox is over the taskbar or maximized, with the "Automatically hide the taskbar in desktop mode" option enabled on Windows 10; the taskbar doesn't 'unhide' whenever you hover over it. This screenshot shows Firefox maximized with the 'taskbar' (the 1px high white bar): https://i.imgur.com/Ys63fGN.png This recording shows Firefox not allowing the taskbar to 'unhide' when it's over it: https://i.imgur.com/G4Vy3r5.gif I should also add that I am using Firefox Nightly, this does not seem to be happening on the stable release of Firefox.