similiar issue to https://support.mozilla.org/de/questions/1217013 but not at the bottom, this is on the top happens as soon as firefox was minimized once issue occured since the post 1803 windows insider preview Current Version 10.0.17666 Build 17666 updating firefox to build 60.0 did not solve the issue screenshot attached as you can see the buttons to minimize close and window mode are displayed in the desktop also