Apple followed up on today’s release of iOS 11.2.1 with the tvOS 11.2.1 update for Apple TV.
The over-the-air update is available in Settings → System → Software Update on your fourth-generation Apple TV and Apple TV 4K. If you have optionally enabled automatic software updates in the Settings, your set-top box will be upgraded to tvOS 11.2.1 automatically.
Like iOS 11.2.1, tvOS 11.2.1 restores remote access to HomeKit accessories for shared users. Apple TV had to be updated as well because the set-top box doubles as a hub for remote control of HomeKit-compatible smart home accessories from the Home app for iOS.
HomeKit suffered from a vulnerability that permitted unauthorized access to HomeKit devices, such as smart locks, blinds and more. Although Apple fixed the bug server-side last week, it temporarily disabled remote HomeKit access.
tvOS 11.2.1 has now restored that functionality.
The security content of tvOS 11.2.1 is listed in a support document on Apple’s website.
You can grab Apple TV firmwares from iDownloadBlog’s Download page.