Sounds like either malware/trojan hijacking, which could be nasty. As no-one else is reporting this issue, and I've never had a problem (other than the odd dead link), the problem must be with your machine.
I have Kaspersky, but even they recommend using Malwarebytes's anti malware free edition from HERE if you think you have a trojan. It's free, so nothing to lose, and it can't hurt :)