They can't be too critical as I have just run CCleaner (as a test) and checked the avast antivirus option in Applications and it has removed those folders and the main avast_ash2.
I will run/refresh the software updater and see if they are regenerated.
EDIT: Refreshed it and they didn't regenerate. Interestingly software updater was reporting out of date software for FF 40.0.3, which is the current regular release and nothing from the FF UI, about firefox, reporting up to date.