iOS 11.4 (build 15F5071a) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2018-05-07T17:11:39Z. The update package is 197.85 MB. 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: bd0c5e02f843e7abbd2da40da3aeb3de5d6a5981.zip.