The OS X Mountain Lion v10.8.2 update is recommended for all OS X Mountain Lion users and includes new features and fixes.
Updating your system
You should back up your system before installation; you can use Time Machine.
Do not interrupt the installation process once you have started to update your system.
You may experience unexpected results if you have third-party system software modifications installed, or if you've modified the operating system through other means.
Choose Apple () menu > Software Update… to check for the latest Apple software via the Mac App Store, including this update.
Other software updates available for your computer may appear, which you should install. Note that an update's size may vary from computer to computer when installed using Software Update. Also, some updates must be installed prior to others.
You can also download the manual update installer. This is a useful option when you need to update multiple computers but only want to download the update once. These versions of the standalone installers are available from Apple Support Downloads.
Additional Information
This update is recommended for all OS X Mountain Lion users, and includes new features and fixes:
Facebook
Single sign on for Facebook
Adds Facebook as an option when sharing links and photos
See Facebook friends' contact information and profile pictures in Contacts
Facebook notifications now appear in Notification Center
Game Center
Share scores to Facebook, Twitter, Mail, or Messages
Facebook friends are included in Game Center friend recommendations
Added Facebook "Like" button for games
Challenge friends to beat your score or achievement
Other new features
Adds Power Nap support for MacBook Air (Late 2010)
iMessages sent to your phone number now appear in Messages on your Mac*
You can now add passes to Passbook (on your iPhone or iPod touch) from Safari and Mail on your Mac*
FaceTime can now receive calls sent to your phone number*
New shared Reminders lists
New sort options allow you to sort notes by title, the date you edited them, and when you created them
Dictation now supports additional languages: Mandarin, Cantonese, Spanish, Korean, Canadian English, Canadian French, and Italian
Dictionary app now includes a French definition dictionary
Sina Weibo profile photos can now be added to Contacts
* Requires iOS 6
General fixes
The OS X Mountain Lion v10.8.2 update also includes general operating system fixes that improve the stability, compatibility and security of your Mac, including the following fixes:
Adds an option to discard the changes in the original document when choosing Save As
Unsent drafts are now opened automatically when launching Mail
Receive Twitter notifications for mentions and replies from anyone
URLs are shortened when sending tweets from Notification Center
Notifications are disabled when AirPlay Mirroring is being used
Adds SSL support for Google searches from the Smart Search Field in Safari
Adds a new preference to have Safari launch with previously open webpages
Resolves an issue that may cause the "Enable Autodiscover" checkbox to always remain checked
Enables access to the Mac App Store when Parental Controls are enabled
Support for @icloud.com email addresses
Resolves a video issue with some VGA projectors when connected to certain Mac notebooks
Addresses an issue that may prevent Active Directory accounts from being locked out
Resolves an issue that may cause the policy banner to re-appear prior to logging in
Improvements to SMB
Addresses an issue with NIS users when auto-login is enabled
Addresses an issue in which the Keychain may not be accessible
Ability to pre-authenticate a FileVault protected system
Addresses an issue that may cause Xsan to not automatically start after migrating from Mac OS X Snow Leopard
