Build 12D65 comes exactly one week after build 12D61. As with build 12D61, build 12D65 continues to ask developers to focus on AirPlay, AirPort, Game Center, Graphics Drivers, and Safari.
Registered developers can download the update on Apple's Developer Page.
Update: According to 9to5Mac, the new build fixes the file bug that recently made headlines.
This post originally referred to Build 12D65 as the tenth developer seed of OS X 10.8.3 when it was actually the ninth seed.