Following its weekly release schedule, Apple's latest beta build 13D61 asks testers to continue to focus on graphics drivers, audio, Safari, Mail and Contacts & Calendar syncing over USB in iTunes. The areas of interest are identical to last week's OS X 10.9.3 Mavericks beta build 13D55.
The most recent build comes two weeks after Apple decided to open up the beta testing process to all Mac users via the Beta Seed Program, a major change to its operating policies. It is unclear how the new program has affected beta rollouts.
Past betas of the forthcoming OS X Mavericks 10.9.3 supplemental update introduced support for scaling that doubles pixels for 4K monitor output, hinting at a so-called "Retina" output mode for late-2013 MacBook Pro with Retina display.
With the latest Mavericks software, Apple is thought to be nearing the final stages of testing before a public release.
As for Safari, Apple has seemingly included minor modifications to OS X compatibility born from changes made through the ongoing 10.9.3 testing process.
Developers -- and users signed up for the Beta Seed Program -- can download Mavericks beta build 13D61 and accompanying Safari 7.0.4 Seed 1 from Apple's Developer Portal or via Software Update.