I've had PriviDog installed for sometime now - part of Comodo Firewall. Not really thought too much about it, no advertising noticed anywhere and it appeared to be blocking lots of tracking cookies etc.
Firefox popped up tonight with a warning with a tick box to disable the software and as I was sort of aware (without fully understanding) negative reports on the internet I disabled it. Firefox started reporting all the sites I visit including my banking as untrusted with possible forged certificates.
After updating Firefox from 35.1 to 36, everything is back to normal. I don't have the technical knowledge to know how bad PriviDog potentially was except for targeted advertising (which I didn't get any) so, I don't know if by disabling it if I've improved my safety and privacy