Could it be real? The impenetrable browser fortress, Firefox, has a security hole, gasp!
Sarcasm aside, the hole has been plugged - a response time of less than day, I believe.
Now, it could be argued (unreasonably) that this is actually an error in Windows, since Firefox correctly passes unknown schemas along to the OS, and the OS is the culprit that simply executes them, but I digress. Let this be a reminder that no system is completely safe, some are safer than others though.