Despite setting Cookie to remove cookies on a timed basis (and on quit), I continually found cookies listed in Firefox (using FF prefs) that should have been removed.
I couldn't figure out why so I deleted Cookie and then reinstalled from the App Store. Now no cookies are appearing in Cookies list - favourite or otherwise - and the app doesn't appear to be doing anything. There are still a shed load of cookies listed under Ffox prefs.
What's going on? I suspect it may be something to do with sandboxing as I run in a user account.
One other point. Where is the file to import previous favourites? The reinstall 'knows' there is one but I can't find it.