https://wccftech.com/ios-12-5-3-and-ipados-12-5-3-for-iphone-6-ipad-mini-3-and-more-also-available-for-download/

If you have an iPhone 6 or older device, including the iPad mini 3, mini 2 or Air 1, then you can download iOS 12.5.3 and iPadOS 12.5.3.

Apple released a handful of software updates a while back. Among them were iOS 14.5.1, iPadOS 14.5.1, macOS 11.3.1 Big Sur and watchOS 7.4.1. All of them have one thing in common: they feature important security fixes.