iOS 11.3 (build 15E5211a) is an official Apple over-the-air update for the iPhone 8 (GSM), released on 2018-03-12T17:05:42Z. The update package is 289.95 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: c0ef940363dd731c6213b6d3612c4dd89b7e7ecf.zip.