It's a system wide infection caused by a rootkit from the ZAccess family, most likely the ZAccess.fxd variant. It doesn't matter which browser you use. Too bad Avast doesn't have a fix for it since it's one of the most wide spread infections at the moment. Please correct me if I'm wrong.
First, use TDSS or ZeroAccess removal tools to remove the core components of this infection. TDSSKilkler is probably the most popular one but sometimes it fails to remove malicious memory modules, so the infection comes back once you restart your PC.