There is another recent question that is similar, 'Restart to update window/message reappears everytime Firefox is started.': I installed firefox on the original admin account (say, admin1), created a new admin account (say, admin2), and when I got a message in admin2 to restart firefox to install an update, I was asked for my admin password, but had no way of knowing whether it was a malicious request. So, I logged in as admin1, saw the same update, which installed itself without prompting for the admin password, and then switched back to admin2. Now, as soon as I start firefox, I get a message asking whether I'd like to restart firefox now or later, but when I click 'Restart Firefox', it starts up again and shows me the same message.