iOS 11.4 (build 15F79) is an official Apple over-the-air update for the iPhone 6s+, released on 2018-05-29T17:16:44Z. The update package is 268.21 MB. This is a delta (partial) update that requires 11.3.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 21dd4b09927f599b93c745325647c7a79ec9b23d.zip.