Apple today seeded build 12D54 of OS X Mountain Lion 10.8.3 to developers
From MacRumors:
Apple Seeds Build 12D54 of OS X 10.8.3 to Developers
10.8.3 was first seeded to developers in November. Build 12D54 comes just eight days after build 12D50, and like the previous build, contains no known issues or features. Build 12D50 brought only minor changes, and asked developers to focus on testing AirPlay, AirPort, Game Center, Graphics Drivers, and Safari.
Apple Seeds Build 12D54 of OS X 10.8.3 to Developers