https://arstechnica.com/gadgets/2019/07/apple-releases-ios-12-4-watchos-5-3-macos-10-14-6-and-more/

As it often does, Apple has released updates for all of its device operating systems at once. iOS 12.4, watchOS 5.3, macOS 10.14.6, and tvOS 12.4 all arrive on supporting devices today.