https://arstechnica.com/gadgets/2020/03/apple-releases-macos-10-15-4-watchos-6-2-and-ios-ipados-and-tvos-13-4/

Earlier today, Apple continued its tradition of updating all of its operating systems at once. The day brought major new feature releases to iOS, iPadOS, macOS, watchOS, and tvOS. The iOS, iPadOS, and tvOS updates are numbered 13.4, Apple Watches got watchOS 6.2, and Macs saw the release of macOS Catalina 10.15.4.