Apple has begun testing Mac OS X 10.5.3, releasing the software to its developer community for widespread testing.

The upgraded OS bundles over 75 fixes and first began to appear with developers on Thursday night. System components addressed in this release reportedly include: AddressBook, AppleScript, Audio, Back To My Mac, Dashboard, Dock, DVD Player, Finder, Graphics, iCal, Mail, Portable Home Directories, Printing, Rosetta, Spaces, Spotlight, Time Machine, and VoiceOver.

The release also implements patches and security improvements across system components. It's not known yet when Apple will ship the latest system update.

Apple shipped its last Leopard update, Mac OS X 10.5.2, in February. The update offered an extensive collection of fixes and patches across the OS and updated Stacks with the addition of a List and Folder view option and introduced an updated background for Grid view. It also added a menu bar for accessing Time Machine.