iOS 11.4 (build 15F5071a) is an official Apple over-the-air update for the iPhone 7 (GSM), released on 2018-05-07T17:11:55Z. The update package is 258.18 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: b597fa0d0777c58018d9892c927f68ae1fe498f3.zip.