tvOS 8.4.2 (build 12H606) is an official Apple over-the-air update for the Apple TV 3 (2013), released on 2016-12-12T19:33:12Z. The update package is 16.71 MB. This is a delta (partial) update that requires 8.4.1 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 84e2334f50b5accedbe42d6d8067efa9b48f97bf.zip.