Abra um terminal ( Ctrl + Alt + T ) e execute:
firefox -safe-mode
Não se esqueça de fechar qualquer instância do Firefox antes de executar este comando.
Consulte aqui para mais informações.
Ou mostre todas as opções via
firefox --help
Usage: firefox [ options ... ] [URL]
where options include:
X11 options
--display=DISPLAY X display to use
--sync Make X calls synchronous
--g-fatal-warnings Make all warnings fatal
Firefox options
-h or --help Print this message.
-v or --version Print Firefox version.
-P Start with .
--profile Start with profile at .
--migration Start with migration wizard.
--ProfileManager Start with ProfileManager.
--no-remote Do not accept or send remote commands; implies --new-instance.
--new-instance Open new instance, not a new window in running instance.
--UILocale Start with resources as UI Locale.
--safe-mode Disables extensions and themes for this session.
--jsconsole Open the Browser Console.
--jsdebugger Open the Browser Toolbox.
--start-debugger-server [port|path] Start the debugger server on a TCP port or Unix domain socket path. Defaults to TCP port 6000.
--browser Open a browser window.
--new-window Open in a new window.
--new-tab Open in a new tab.
--private-window Open in a new private window.
--preferences Open Preferences dialog.
--search Search with your default search engine.
--recording Record drawing for a given URL.
--recording-output Specify destination file for a drawing recording.
--setDefaultBrowser Set this app as the default browser.
-g or --debug Start within debugger
-d or --debugger Specify debugger to start with (eg, gdb or valgrind)
-a or --debugger-args Specify arguments for debugger
