Despite the fact that recently hosted the full release first update for iOS 13, while the cupertinos are not yet ready to stop working on the previous version of its mobile operating system. Tonight they released a small update for iOS 12.4.
IOS 12.4.2 is designed primarily for devices that cannot upgrade to iOS 13. It kupertinovtsy fixed various critical bugs and minor issues, and paid attention to the security of the system. More specific information about the changes, no.
Along with iOS 12.4.2 cupertinos also released a small update for their other platforms. It is reported that in watchOS 5.3.2 macOS 10.14.6 have fixed some minor bugs and increased security operating systems.
Judging by the user feedback, any changes after installing the updates were noted. Devices operate about the same speed as before.