The first of many, apparently.
If you purchased the latest Xbox console last month, you'll be seeing the console's very first system update today. This is a required update and was made available by Microsoft at 5pm PT on Tuesday, December 10.
Microsoft's Larry Hryb wrote in his official blog that the update addresses SmartGlass issues as well as issues with players rejoining games in multiplayer and issues with inconsistent notifications. There's also fixes for dashboard problems, an update for the wireless networking driver, and improvements to Xbox One’s TV, system update, and content update services for scaling over time.
Hryb says the folks at Redmond have 'quite a few' updates planned for the next year based on community feedback. Those with Instant On will see the update download in the background and the update will be applied the next time they turn on their console. If you don't have Instant On activated, you'll have to download and apply the update manually. You can do this starting tomorrow, December 12, at 2am PT.