Apple released iOS 15.3 and iPadOS 15.3 on Wednesday. It does not appear to be a particularly major release. The Software Update Notes say “it includes bug fixes and security updates” and is recommended for all users.
Security Updates in iOS 15.3 and iPadOS 15.3
Although there are no new features included in the release, it is important to keep up with the latest security updates. To install it, go to Settings > Software Update and follow the on-screen instructions. The same is true on an iPad. You may be required to put your device on charge and wait for it hit 50 percent battery to be able to install the update.
watchOS 8.4 has also been released and includes a fix for a bug that affected charging.