Please do not block my browsing session just to force me to restart! Let me restart when I want to. For security reasons, I'm almost always browsing in Private Mode, and as such, logins and passwords are not saved. So when I'm forced to restart because of an update, I have to save my current tab session, reopen them after FF has restarted, and re-login to every site I was using—many of which require 2FA, so it's extra annoying.
This is bad UX! Put a notification, or even a whole separate tab telling me I need to restart. But don't block out everything I was doing. Even Windows doesn't do this...