HOW TO GET IT:
• If your console is in Instant-On mode and you have been selected to receive the update, it will download and install the update and reboot to standby.
• NOTE: Once the update is available to you, you can manually begin the update by launching the Guide and navigating to All Settings > System > Updates.
• If your console hasn’t downloaded and installed the update by 3:00 AM PST 1/31/2018 (12:00PM GMT 31/1), you will be prompted to do so at that time.
• This update has a shorter than usual amount of time before it becomes mandatory.
OS version released: rs3_release_xbox_dev_1802.180129-1625
Available: 10:00PM PST 1/30 (6:00AM GMT 31/1)
• Installation Progress in Guide
In-progress installations are now visible from a tile at the bottom of the Guide. When selected, this tile opens a new interface showing items in the queue and their status, and allowing some basic functions like pausing or cancelling the installation.
Fixed an issue which caused some elements in Profile to appear misaligned.
• Home and Dashboard
Resolved an issue which sometimes caused unexpected crashes.
Miscellaneous fixes and improvements.
• Games Installation
Games that are installed fail to launch.
Workaround: If the games are installed to an external drive please copy the game to the internal drive or attempt to delete the title and redownload to fix the launch error.
We are investigating the inaccurate RGB colors that have been reported when displaying in 4K HDR mode when playing a UHD disc.
• The left and right navigation for selecting date and time during Tournament creation is currently reversed when the console language is set to Arabic or Hebrew.
• Left and right navigation in Tournament twists is reversed when the console language is set to Arabic or Hebrew.
• Left and right navigation in the bracket view of Tournaments is reversed when the console language is set to Arabic or Hebrew
• Avatars on Home
Users wishing to represent themselves as an avatar can do so by changing their settings under My profile > Customize profile > Show my avatar.
Quelle: Xbox Insider Forum