https://arstechnica.com/gadgets/2021/03/apple-addresses-webkit-security-flaw-with-ios-and-ipados-14-4-2/

Today, Apple began rolling out iOS 14.4.2, iPadOS 14.4.2, and watchOS 7.3.3, and the company issued an advisory to users to upgrade as soon as possible. Like iOS/iPadOS 14.4.1 before it, this update addresses a security flaw.

Additionally, Apple released a similar security update—12.5.2—for older devices like the iPhone 5S or 6 that cannot run iOS 14.