Safe mode is now (sometimes at least) called troubleshoot mode and it should cease to apply when you exit the browser. https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode I have never had to deal with a browser 'stuck' in that mode. If it continues, try clearing the cache. https://support.mozilla.org/en-US/kb/how-clear-firefox-cache If that doesn't work, try creating a new profile. https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles

Note that you might be holding the shift key while starting Firefox if you end up in Troubleshoot Mode. *Windows: hold down the Shift key while starting Firefox to start in Troubleshoot Mode *https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode