You have to update MSN Messenger to the latest version for the vulnerability to be fixed.
The reason that we bring this up is that WindowsUpdate doesn’t update MSN Messenger as it isn’t a standard part of Windows.
Although there is an automatic update notification system present in MSNM, it can take a long time for it to actually inform the user about a newer version.
Given the severity of the vulnerability we recommend everyone to update MSN Messenger manually. You can get the latest version at http://messenger.msn.com/Download/.