OS X 10.6.6 fixes a flaw in PackageKit, a software installation and updating tool. Mac users will be able to download and install apps directly from the App Store using their iTunes accounts. The App Store is Apple s move to extend the iTunes buying experience to the Mac platform. The opening of the Mac App Store opens up what has become a favorite new attack vector: malicious applications and malware-laced fake apps. Apple, Google and BlackBerry all have found themselves with malicious apps in their mobile-phone app stores in recent months.
Source: https://threatpost.com/apple-releases-os-x-1066-one-bug-fix-mac-app-store-010611/74825/