Lots of iOS users are getting excited for iOS 13, which is expected to launch to the public next month. Before then, though, Apple has released a new iOS 12 update.
iOS 12.4.1 is now rolling out. This is a smaller update that Apple says "provides important security and stability updates." You can grab it by going into Settings > General > Software Update on your iOS 12 device.
Apple isn't divulging exactly what "security and stability" improvements that are included in iOS 12.4.1, but it's speculated that the update is meant to fix a vulnerability that allowed users to jailbreak iOS 12.4. That vulnerability was patched in iOS 12.3 but was accidentally unpatched in iOS 12.4, and so it's possible that this iOS 12.4.1 update plugs that hole again.
Also released today is watchOS 5.3.1, which Apple says "provides important security updates". You can install it by launching the Watch app on your iPhone and then going into "General" and then tapping "Software Update".
UPDATE: Apple has posted a support document that confirms that the iOS 12.4.1 update addresses a vulnerability in which "a malicious application may be able to execute arbitrary code with system privileges." The company adds that "a use after free issue was addressed with improved memory management."