https://arstechnica.com/gadgets/2018/06/apple-releases-macos-high-sierra-10-13-5-with-messages-in-icloud-support/

Today, Apple released the latest update for macOS. High Sierra 10.13.5 primarily adds Messages in iCloud support, but it also includes some enterprise and security updates. Users of supported Macs can download and install it from the Mac App Store now.