Apple on Thursday released the first beta seed of OS X 10.9.3. It's now available for download by those registered with Apple's Mac developer program. The build number for this release is 13D12.
It was only last week that Apple publicly released OS X 10.9.2, which fixed an important SSL security problem, added FaceTime Audio, made improvements to Mail and more.
Apple's release notes for OS X betas are covered under their non-disclosure agreement with developers, so we won't report on the contents. But if you're a registered Mac developer, get yourself over to Apple's developer site and check it out for details.