Apple just seeded a new development release of OS X Mountain Lion 10.8.5, build 12F20 on it’s Developer page today. It includes a combo updater, a delta (just changes) updater, and a note describing the changes in the new seed.
The seed note says that the focus areas of this current seed are, like previous seeds, Wi-Fi, Graphics, and Wake from Sleep. In addition, this seed also focuses on PDF Viewing and Accessibility as well as Mobile Device Management.
If you’re a developer working on Mac apps that need to be compatible with OS X Mountain Lion, go ahead and head over to Apple’s Developer page and grab yourself a copy of one of the updaters, and have at it.
Source: Apple Developer