said by HowDoesItWork :
So it could infect you without requiring any form of consent from the user? Now that is weird. For IE, I wouldn't be surprised, but if Firefox or Opera would do the same, that would be strange. I'm further confused because mysec on the previous page posted that with Opera, it does pop up a download prompt, and if you cancel the download, it can't infect you.
Part of the infection can be done with PDF documents. Adobe even put out a warning that they wouldn't have a fix for a month.