Apple today seeded build 12F23 of OS X 10.8.5 to developers, offering a fifth version of the next Mac operating system update for testing. The release comes one week after the appearance of the previous beta of OS X 10.8.5, build 12F20.
Testing on OS X 10.8.5 comes as Apple is also continuing work on its next major version of OS X, Mavericks. Apple has already seeded three developer previews of OS X Mavericks and has announced that it will launch the new operating system to the public this fall.
Article Link: Apple Seeds OS X 10.8.5 Build 12F23 to Developers