Comment 1 for bug 174945

it will BUT not in usermode u have two choices:

1.)close firefox and uninstall it thru the synaptic package manager

or

2.) close firefox open up a terminal and type sudo firefox & input ur password - don't worry nothing showing up is normal, just type the password as usual and hit enter, now go to the add-ons and the uninstall option should now NOT be greyed out and click uninstall and restart firefox - click the button and then once back up we don't want to be running in root mode so then exit out of firefox - important restart firefox in root mode or it will not go away until next time, and restart it in normal user mode, By going to internet --> firefox