It is actually a photo posted from one of your infected friend on your wall.
They gave a small description about- How it works:
"For those unfamiliar with Facebook (is there anyone other than me in that set?) the thumbnail of the worm's infective page is a link to the page. The worm's objective, of course, is that others viewing the victim's wall will click the link, and as they are logged into Facebook, the worm will propagate its link to that victim's wall, and so on...
This worm uses what is technically known as a CSRF (Cross-site Request Forgery, also called XSRF) attack. A sequence of iframes on the exploit page call a sequence of other pages and scripts, eventually resulting in a form submission to Facebook "as if" the victim had submitted a URL for a wall post and clicked on the "Share" button to confirm the post."
So, be careful when you find some hot image on your wall which is telling you "clicking da button". Avoid such type of hot photos posted by an infected friend. And if you are daily addicted to Facebook, you are specially asked for not to click any suspicious links or any hot image link posted on your wall. This attack can highly effect your Computer or Account.
