iPadOS 8.4.1 (build 12H321) is an official Apple over-the-air update for the iPad 4 (GSM), released on 2015-08-13T18:05:09Z. The update package is 347.68 MB. This is a delta (partial) update that requires 8.1.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: e3b3f6e76061ce25410d02d0e6e8ddd1bb8e556c.zip.