https://wccftech.com/macos-high-sierra-10-3-3-beta-1-released-developers/

In a rather surprising move, Apple has released for download macOS High Sierra 10.13.3 Beta 1 for download.

Having updated its lineup of software just recently for the public, including macOS High Sierra 10.13.2, Apple has now released macOS High Sierra 10.13.3 Beta 1 for registered developers. So, if you have a paid developer membership with Apple, you can head straight over to the developer portal and download the latest release.