Ah! This thread is just what I was looking for!
For months now, once in a while, I get a complete redirect to pcupgradenow (via redir.aitrkng.com) saying Chrome or whatever is out of date... download this update! And then attempting to close/leave the page pops up a text box asking Are you SURE???. This has only ever happened to me on Craftster and I am absolutely certain that I am not infected by this particular malware. I don't want to post the full urls here, but I can PM them to someone if it helps.