My friend has a computer that since yesterday has started to constantly open a popup: http://www.planetside2.eu/en/landingpage/402
That appeared yesterday and today, and the history has been cleared out 100%. They are using Firefox.
Why is this happening? I've been assured they never installed any programs and that they have the latest Kaspersky Internet Security installed.
Any ideas a)how it got there and b) how to stop it?