iOS 12.3 (build 16F5129d) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2019-04-08T17:05:06Z. The update package is 361.39 MB. This is a delta (partial) update that requires 12.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 128ce2cce2dc400c6abeb26756ccdc355460dfa1.zip.