For the last few updates, Firefox has caused the same issues on all four of our Macs (Pac Pro, MacBook Air, MacBook Pro & Mac Mini). All of them are currently on the… (read more)
For the last few updates, Firefox has caused the same issues on all four of our Macs (Pac Pro, MacBook Air, MacBook Pro & Mac Mini). All of them are currently on the latest OS X (El Capitan 10.11.3). The update appears to install and work, but a second icon appears in the dock. On trying to quit Firefox, it won't quit and then (even worse) the Mac will not close down. 'Shutdown' and 'Restart' do nothing. Force quit shows both versions of Firefox, but neither can be 'force quitted'. The only way to shut down the Mac is to switch it off at the wall. On re-starting the Mac, Apple informs that it was not closed down properly. However, after all this, Firefox then does work properly. I think it is installed correctly in the Applications folder, and I have (on one Mac) completely refreshed Firefox. but this hasn't helped. Is this a known bug, or am I doing something wrong on all four Macs? Thanks, in advance, for your help.
Please also see:
Further details relating to known bug that is under investigation & may cause this #answer-860313 ~J99