Today, Apple released iOS 13.4.1 and iPadOS 13.4.1, introducing a few key fixes. The update is the 12th since iOS 13 and iPadOS 13 were originally released, and they're not the last either, with version 13.4.5 currently in beta.
Both updates have a handful of key bug fixes. For one thing, there was an issue that causes iOS 13.4 devices from being in FaceTime calls with users on iOS 9.3.6 and earlier, and OS X El Capitan 10.11.6 and earlier. This was resolved on both iOS and iPadOS.
Another fix for both platforms is for a bug with choosing Bluetooth from the quick actions menu, causing it to fail. Finally, there's one fix that's exclusive to iPadOS, and more specifically, the fourth-generation 12.9-inch iPad Pro and second-generation 11-inch iPad Pro, fixing an issue that caused the flashlight to not turn on when it was accessed through Control Center.
These updates do not include any security fixes, at least according to Apple. iOS 13.4.5 should be the next update, and that will likely arrive in a few weeks or so, followed by betas for iOS 14 and other major updates after the WWDC keynote in June.