Hi, ya can be a pain. Have you checked the Start Button and the Start-up folder there ? Also can check Settings --> Apps__>Default Apps and see if Firefox is set to open something there. Note : Firefox 62.0 release tomorrow. Can do a clean reinstall if so wish : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer Reinstall with Current Release Firefox 62.0.0 with a Full Version Installer *https://www.mozilla.org/firefox/all/ Wait till is up. *Help --> About; to update * Select Version & language now : https://archive.mozilla.org/pub/firefox/releases/62.0/ Please let us know if this solved your issue or if need further assistance.

See also: *https://support.mozilla.org/en-US/kb/firefox-starts-automatically-when-i-restart-window *[/forums/contributors/713113] Pushed out to 10% release users - Firefox starts automatically when I restart Windows | SUMO community discussions