Apple has released tvOS 9.0.1 for Apple TV. The update can be downloaded over the air via Settings> System> Software Updates. The update can also be downloaded from the website Apple, it weighs 922 MB.
tvOS 9.0.1 has a build number of 13T402. All users with tvOS 9.0 installed are encouraged to upgrade. For previous generations Apple TV no updates were released.
The list of changes is unknown, but they are most likely aimed at improving the security and stability of the system. As soon as something becomes clear, the post will be updated.
If you want to download the update yourself and install it via iTunes, you can do it here. Remember that you need a USB Type-C cable for this operation.
Have you already updated? If you find something new, let me know in the comments.