http://wccftech.com/apple-seeds-macos-10-13-1-and-tvos-11-1-beta-4-to-developers/

Today, Apple has seen fit to release the fourth beta of its upcoming macOS High Sierra 10.13.1 and tvOS 11.1 to developers for testing purposes. The update comes less than a week after the company rolled out the third beta of macOS 10.13.1. Apple announced its macOS High Sierra and tvOS 11 at the WWDC event this year. The operating systems boast a bevy of new additions complementing both visual aspects as well as in the performance department. So let’s dive in to see some more details on the beta 4 of macOS High Sierra 10.13.1 and tvOS 11.1.

At the time of publication, there are no new forward-facing features discovered in the macOS 10.13.1 beta update. However, we will let you guys know as soon as something is found. At this point in time, we can say that the update focuses on bug fixes and performance enhancements as well as security updates and other under the hood changes.