Recently I switched from a horizontal taskbar configuration to a vertical one in Windows and have discovered some odd behavior. When Firefox is maximized a grey bar displays at the bottom of my secondary screen. These displays are stacked vertically with the "Extend desktop to this display" option in Windows settings. This seems to be covered by the taskbar when horizontal at the bottom of the screen. [https://imgur.com/a/FYbiDBo Here] is an image of what I see. Some details as to my setup: * Multi-display setup (laptop screen and two monitors) and extended display configuration (one display arranged above another) * All displays support the same resolution (1920x1080) and have the same scaling (100%) Some troubleshooting steps I have taken: * Restarted Firefox, Windows Explorer, Desktop Windows Manager, as well as my the laptop itself * When tested with other applications maximized this does not occur (Microsoft Edge, Chrome, Spotify, Notepad++, etc) * Updated display adapter driver to latest version * Reproducible on my secondary machine with the same configuration I have not been able to find this behavior mentioned in the Firefox or Windows support forum(s) or other places like Reddit. Has anyone come across this issue before and/or been able to determine if this is a known issue Firefox?