Apple has updated macOS, iOS, iPadOS, tvOS, and its HomePod firmware.
macOS Catalina 10.15.4 can be downloaded from the Mac App Store for free using the Update feature in the System Preferences app.
iOS and iPadOS have been upgraded to version 13.4. They can be over-the-air in the Settings app. To access the updates, go to Settings > General > Software Update.
watchOS 6.2 can be downloaded for free through the dedicated Apple Watch app on the iPhone by going to General > Software Update and following the instructions.
tvOS 13.4 can be downloaded over the air through the Settings app on the Apple TV by going to System > Software Update. Apple TV owners who have automatic software updates turned on will be upgraded to tvOS 13.4 automatically. The upgrade provides support for the Powerbeats 4 earphones along with of bug fixes and improvements.