Sequence: Get messaged "Go To http://www.masenko-media.net/cool.html NoW !!!" or something similar with another URL. Follow the link. That webpage contains malicious code which gets your messenger contacts and sends a similar message to your contacts. It looks like it uses a vulnerability in formmail.pl as well, although I'm not exactly sure how (I'm not an expert in ECMAscript, sorry, and I have no systems that could possibly be affected by this to test with). I'm sure some of our readers can provide more information in the comments below.
There appear to be several webpages which carried the infected code, not just masenko-media.net. Some webmasters are already taking them down.
Sophistication: moderate. Damage: only your pride.
Solution: probably the latest mega-patch for Internet Explorer will fix the Microsoft bug that allowed this.
Risks: obviously, the code could have done worse than just messaging your contacts. With Microsoft making "messaging" an integrated part of the operating system, any flaws in it can be exploited to affect millions of people instantly, so it is a high-value target. Does it have commensurate high-strength security?