iOS 11.4 (build 15F5079a) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2018-05-17T17:02:26Z. The update package is 248.89 MB. This is a delta (partial) update that requires 11.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 06c7d92768459678f69d5cde6da92aaa10e4a9d8.zip.