User interaction is required to exploit this vulnerability in that the target must open a malicious file.
The specific flaw exists in the handling of internet enabled disk image files. When a specially crafted Menu Extras plugin is included in the disk image, it is executed without further interaction allowing for arbitrary code execution under the context of the current user.
Patch Availability:
Apple has issued an update to correct this vulnerability. More details can be found at: http://support.apple.com/kb/HT4077