More information about the exploit and the updates that the Invision Board team have made to counteract it can be found in this board pasting.

Unfortunately, there has also already been an incident with the exploit, causing the boards of "a large company" that was using it as a forum for its customers. Links started showing up that were causing problems, redirecting users to another server's page that pushed the bad .wmf file to them.

If you are running an Invision Board version before 2.1.6, it is stringly suggested you upgrade.