iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad mini 4 (WiFi), released on 2018-04-24T17:07:10Z. The update package is 705.17 MB. This is a delta (partial) update that requires 11.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 7a859e0a6ed9d2bdd9ab50e8e2bf333d06d81621.zip.