A Neowin member wishing to remain anonymous has alerted us that users can generate their own flash movies and send them across MSN Messenger. As flash movies can open other things on the system such as Internet Explorer, this could be fatal. As MSN Messenger 7 is only beta and isn't available publically this isn't a major exploit but it does show that added features to a product like this makes it less secure and more open to attack/exploit.If you are using or planning to use the MSN 7 beta then please be aware of this!
MSN Messenger 7 is beta and is available in copies floating around the internet. We strongly advise members not to use the current beta until this flaw has been resolved. MSN Messenger 7 effectively opens your system up to allow a hacker to run numerous tasks on your machine.
Source: NeoWin