Earlier this week, Apple released Mac OS X Mountain Lion 10.8.3. This maintenance upgrade is recommended for all Apple customers running Mountain Lion on their Macintosh.
You can upgrade your Mac by clicking on the Mac App Store icon in the Dock and then clicking the Updates icon on the top right of the App Store toolbar. If you are running the upgrade on a MacBook, MacBook Pro, or MacBook Air, it is strongly recommended that you plug in your power adapter before starting the upgrade.