Just a week after the last OS X Mountain Lion 10.8.3 beta was released, Apple has issued a slightly newer build
to developers and testers. The new version comes with no changes to the release notes or any known issues, but the previous beta 12D54 was noted as making improvements to the Wi-Fi component of OS X. The new version is build number 12D58, and is likely to continue cleaning up code and squashing bugs found in earlier releases. The incremental change in build numbers suggests that release is forthcoming.