A company called Pentest has released an advisory about a major vulnerablity in widespread bluetooth software, used both on Windows PCs and PocketPC handhelds.
This vulnerability in WIDCOMM Bluetooth Connectivity Software allows arbitrary code execution with priviledges of the user that is currently logged in. Which means that in theory, using this vulnerability it would be possible for a malicious party to write a wireless worm that spreads between PCs or PDAs using Bluetooth over the air. Worms like this could spread very fast, especially in an environment like a seminar or a conference.
This vulnerability is fairly serious since WIDCOMM software is very widespread and seems to be used in most Bluetooth dongles and Bluetooth-enabled computers.
WIDCOMM has not yet released a software update that would fix the vulnerability, so in the meanwhile users are recommended to set their Bluetooth-enabled devices into non-discoverable mode and keep bluetooth switched off when you don't need it.