How to force to restart firefox in a clean way?

Many times when I upgrade the system under Linux, firefox pops up a window suggesting to restart the program in order to make effective all the changes.

When I ignore that windows because of an urgent duty in a second time I’m not able to find it again.

Of course I know it’s always possible to exit and restart it manually; in Linux to kill the process with pkill firefox && sync && firefox &, with or without a brutal -9.
In a similar way in Windows it is possible to use the Task Manager…

What I was searching for is an internal solution, a clean one, possibly system independent.
How to force to restart firefox in a clean way ?

ps> It is possible that when updated external third parties programs firefox will not prompt for restarting, even if it should be recommended.

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