Apple on Tuesday released second betas of iOS 10.2.1 and macOS 10.12.3 to the developer community, continuing to leave many of the changes made a mystery.
Both seeds should be available through Apple's developer portal. People who already have one of the prior betas installed can update over-the-air in the case of iOS, or via the Mac App Store's Updates tab.
It's not clear what changes are in either release, as even Apple's official notes for macOS 10.12.3 only mention "stability, compatibility, and security" improvements. Given that and their version numbers, both are likely to focus solely on maintenance.
The initial betas were issued just five days ago, hinting that Apple may be hoping to keep up the intense pace of its last beta cycle. The new releases may simply be limited in scope however, and another possibility is that Apple wanted to clean up bugs before developers break for the holidays.