iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad mini 4 (WiFi), released on 2018-04-24T17:07:08Z. The update package is 1.26 GB. This is a delta (partial) update that requires 10.3.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 80e078f6591cc1a9f8e76475a8e04abe5325cd8c.zip.