Browser hijack.

Yes we are used to seeing spyware hijack the Internet Explorer browser. Those of you that still use IE anyway.

But if you install a Microsoft released a patch for a “critical” vulnerability in MSN Messenger, Microsoft will hijack your browser, ignoring your home page selection and setting the home page to MSN. The patch is mandatory for users of MSN Messenger so you won’t have a choice.

Apparently Microsoft Anti-Spyware takes a similar action.