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 330.4 MB. This is a delta (partial) update that requires 8.1.2 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 46a51e5258e379ca769fb4e82a0468d7c1b4d6b1.zip.