Further expanding on the Mac wireless vulnerability we heard about earlier today, it seems that to be at risk for this, a system must have had third party hardware installed into it. So the culprit in this case is wireless equipment, rather than the operating system or architecture of the Mac. Adding new hardware to a machine is often part of the experience though, leaving plenty of room for people to make mistakes. Unfortunately for the users, the people who found the exploit aren't willing to share what hardware is the culprit and whether or not some cards are not affected:

The problem itself isn't really an Apple problem,' said Maynor, a researcher at SecureWorks Inc., a network-monitoring company. 'This is a systemic problem across the industry.' [...] The MacBook used in the demonstration was not using the wireless gear that shipped with the computer. Instead, they used a third-party wireless card that they declined to name"
While not sharing the details of the exploit is understandable, if there is a risk easily avoided by watching what hardware you buy it would be nice of them to share. Regardless, it's still possible that Apple may decide to create a software workaround, if possible, since it is much easier to fix software than hardware.

Update: More information reveals that the flaw may lie within multiple types of wireless hardware, including Apple-branded hardware, rather than just any random card.