Apple has released a new beta for iOS 12.1.3 and macOS Mojave 10.14.3, along with a second beta for tvOS 12.1.2. The new beta versions are available for developer testing initially, and are typically soon followed by public beta releases.
iOS 12.1.3 beta 2 is said to contain ‘bug fixes and improvements’, though specifics are not yet clear.
iPhone and iPad users enrolled in the iOS beta testing program can find iOS 12.1.3 beta 2 available to download from the Settings app Software Update section.
MacOS Mojave 10.14.3 beta 2 also likely includes a focus on bug fixes.
Mac users participating in the Mojave beta testing program can find the update available now from the Software Update mechanism of MacOS.
iOS 12.1.3 might be a relabeled version of what was the brief iOS 12.1.2 beta, which only went through one beta build before the iOS 12.1.2 update was quickly released for iPhone just a few days ago.
It’s unlikely that any major new features are to be included in iOS 12.1.3 or MacOS 10.14.3, as typically point release updates are aimed at more incremental improvements, security updates, and bug fixes. Apple usually goes through a variety of beta builds before issuing final stable versions of those system software releases.
The most recently available stable builds of system software are currently iOS 12.1.2 for iPhone, iOS 12.1.1 for iPad, and MacOS 10.14.2 for Macs.