User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0 Build ID: 20170803103124 Steps to reproduce: Installed v55 and restarted FF; I have tried restarting FF to see if the problem clears, but it doesn't. Actual results: After update and restart, all other windows (even those normally "always on top", with one exception) will not appear on top of FF window, even if in focus and moved over from my second display. Popups that are triggered by extensions that normally popover now popunder and cannot be reached via <Alt-Tab>. The one exception is the Citicards "Virtual Account Numbers" app, which I can open in my secondary display and then slide on top of the FF window. Expected results: Sliding over in-focus windows from my secondary display to the primary display (where FF is open) should leave the in-focus window on top of the FF window; instead, it slides under the FF window. FF extension pop-ups should popover, but instead popunder.
Component: Untriaged → Widget: Win32
Product: Firefox → Core
Resolution achieved: (1) Reboot the computer. (2) Restart Firefox -- FF will load, but freezes. (3) Use Task Manager's Processes tab to force quit FF process and all subprocesses. (4) Restart FF--this time it works, and the "always on top" problem is resolved. While this particular issue was unique, in my experience, having to do multiple FF restarts and/or system reboots after a FF update is far too common. I can't help but think there's something wrong with the updater process, as I don't have such problems with Chrome or IE updates. That said, I should have thought of this before filing a bug report--my apologies.
This should be investigated, if reliable steps to reproduce can be found. Having to reboot the system is not acceptable step in FF update.
Status: UNCONFIRMED → NEW
Ever confirmed: true
Priority: -- → P2
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