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 1:00 AM PST 12/3/2017 (9:00AM GMT 3/12), you will be prompted to do so at that time.
• NOTE: This update has a shorter than usual amount of time before it becomes mandatory.
OS version released: rs3_release_xbox_dev_1711.171130-1951
Available: 2:00PM PST 12/2 (10:00PM GMT 2/12)
Fixed issues which sometimes prevented users from pressing B to go back when navigating the Store.
• Privacy & online safety
Resolved an issue which caused child accounts with family restrictions to retain the restrictions after graduating to an adult account.
• Party Chat
Fixed an issue which caused some users to lose all party chat audio and voice quality fixes.
AVRs with HDMI-Passthrough should no longer break Dolby Atmos for Home Theater if the TV and console is turned on before the AVR.
We are investigating reports of degraded Wi-Fi- performance. Current workaround that works for some users is to Hard reboot the console (aka hold the power button for ten seconds)
• Games/apps not installing/updating
We are investigating reports of some users cannot install any games or apps. Current workarounds that work for some users is change Wi-Fi networks quickly, plug in an Ethernet cable or to disable IPV6 on your home network.
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.
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Quelle: Xbox Insider Forum