Not only iOS 16.3, Apple also released iOS 12.5.7 and iOS 15.7.3 updates. Both of these updates are for old iPhones.
One of the devices getting the update is the iPhone 5s. This phone was released by Apple in September 2012, meaning it has been almost a decade.
Of course this is amazing! What's more, looking in the mirror on an Android phone, let alone an old 9 year old device, sometimes phones that are over 2 years old don't get security updates anymore.
List of iOS 12.5.7 Compatible Devices
iPhone 5s
iPhone 6
iPhone 6 Plus
iPad Air
iPad Mini 2
iPad Mini 3
iPod Touch 6
iOS 15.5.7 Compatible Device List
iPhone 6s
iPhone 6s Plus
iPhone 7
iPhone 7Plus
iPhone SE
iPad mini 4
iPad Air 2
Need an Update?
The iOS 12.5.7 and iOS 15.7.3 updates address a number of bugs and the Webkit security patch found in iOS 16.
The official iOS 15.7.3 / iPadOS 15.7.3 security page lists five new improvements (compared to 13 in iOS 16.3) - these cover kernel apps, email, maps, and screen time.
The iOS 12.5.7 security page lists only one fix - CVE-2022-42856 - but it is a critical zero-day patch for a vulnerability in Webkit (the engine behind Safari) that was fixed for new devices in December with iOS 16.1.2.
That's why it's recommended that you update iOS 12.5.7 and iOS 15.7.3 as soon as possible.
How to Update
Back up iPhone a first to iCloud , Finder on MacOS , or iTunes on Windows before starting.
Open the "Settings" app on your iPhone or iPad
Go to "General"
Select "Software Update"
Select "Download & Install" when "iOS 15.7.3" or 'iOS 12.5.7' when available