iOS 11.4 (build 15F5079a) is an official Apple over-the-air update for the iPhone 6+, released on 2018-05-17T17:02:28Z. The update package is 275.96 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: 2d9224328f265ac16cb8438e36434af40132f45b.zip.