iPadOS 8.4.1 (build 12H321) is an official Apple over-the-air update for the iPad 4 (WiFi), released on 2015-08-13T18:05:08Z. The update package is 330.37 MB. This is a delta (partial) update that requires 8.1.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: d0e78b85ee7778ee22c7e05f5df013e22314543d.zip.