iOS 12.0 (build 16A366) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2018-09-12T19:10:37Z. The update package is 1.27 GB. This is a delta (partial) update that requires 11.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 3bb841ef33e6e43911bdda9b88dd53e93a1e9664.zip.