Apple released an update today for their Airport wireless cards that addresses multiple vulnerabilities. Those vulnerabilities put all wireless-capable OS X computers at risk of being compromised by an attacker, including the new Intel-based Macs.
Without the update, an Apple computer connected to a malicious "WiFi spot" could potentially be compromised to the degree that an attacker can gain control of the computer and execute arbitrary code.
To get the latest update, simply go on the Apple menu and select "Software Update". Download any updates available.
You can read up on the vulnerability here: