iPadOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPad mini 4 (WiFi), released on 2018-04-24T17:07:11Z. The update package is 608.48 MB. This is a delta (partial) update that requires 11.2.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8482596535d8261945fe9f3323a2b8e1a1eda9cf.zip.