iOS 11.4 (build 15F5079a) is an official Apple over-the-air update for the iPhone 8 (GSM), released on 2018-05-17T17:02:22Z. The update package is 322.76 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: 81de08b98cfb8f808e2ad18fbc6cb1855a58ea42.zip.