It's not all boring security stuff; Apple also added a Genius playlist function. To access the Genius function, just hold down the play/pause button while a song is playing, and a popup menu will allow you to "Start Genius," or add to an on-the-go playlist.
You can download this update by navigating to Settings > Update Software. Alternatively, Apple TV checks on a weekly basis for any new updates. If it finds an update, it will download, verify, and install the new update. You can read more about this update in this Apple support article.
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