Apple has issued a security update for its Apple TV service.

The 2.2 update not only fixes a bug, but also adds a new feature.

The bug, says Apple, means that a "maliciously crafted movie file may lead to an unexpected application termination or arbitrary code execution". Eek.

But the update also introduces the Genius playlist function to Apple TV.

This is a feature of iTunes too, and automatically makes playlists from songs in your library that go well together.

Genius also includes Genius sidebar, which recommends music from the iTunes Store that you don't already have.

Once they have updated, to access the Genius function, Apple TV users just hold down the play/pause button while a song is playing, and a pop-up menu will give you the option to "Start Genius", or add to an on-the-go playlist.

To download the update, hit the settings tab, and then the Update Software option.

Apple TV also checks for updates automatically on a weekly basis so will install 2.2 by itself.