Lately, when browsing fanlistings, I often come across a warning from Avast that the website I'm visiting is infected. I wondered what it was, and saw that more than one domain seemed to be infected. I came across this thread over at TFL Boards, explaining what's going on. In brief: if you use Adobe Reader to open PDF files, make sure to upgrade to the latest version. Actually, the the problem was discovered over 2 months ago. You can read more on the security flaw and its patch.