Xbox Live users are reporting that their real names are being display on the service even if they had it disabled in settings. This is a random mistake although it has opened these users to potential doxing by those who might have an agenda against them.
This issue was first reported on reddit in a thread where multiple users have now verified that their real life username is being display instead of their gamertag. If you have people added on Xbox Live, they might be able to see your real name now even if you have disabled the setting for it, in addition to anyone who can see you playing online in recent players list.
The real name seems to be taken from your Microsoft account so the potential for the damage is there if someone knows it. To disable it, you need to head to the following link and then make sure that name sharing is disabled. If you add a new friend, the setting is usually displayed asking if you want them to see your real name.
Currently, there is no estimate of how many people seem to be affected by it although there are some that don’t have an issue with their account. It is still better to check out your Xbox Live profile setting to make sure that there is no such issue for you.