Hi, strange, please give yourself a quick scan : https://www.malwarebytes.com/ Then 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 60.0.0 with a Full Version Installer *https://www.mozilla.org/firefox/all/ If still a issue : make a new Profile Make and test ...: *https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Give a shout back and can help further.