http://securityresponse.symantec.com/av ... 11173.html
Take this really, really seriously, because this is really, really big.
Symantec (and a few other sources) basically say that every single windows system that uses MSIE is vulnerable to this problem.
heres a writeup on what it does:
http://www.easynews.com/virus.html
the image that displays (!) is basically a WHITE, BLANK IMAGE.
Therefore someone could place this on say google.com, or cnn.com, and mess EVERYONES days up.
The only workaround ive seen for this is to use an alternate browser. i know for a fact that netscape and mozilla arent affected, and opera doesnt seem affected.
edit: there are patches for all of the microsoft operating systems on the symantec write up page. click the link that corresponds to your OS and youll be patched