I started a new server for me and my friend, and set it to friends only so Noone could join, and people that are not on my or my friends list are still able to join our server.
Steps to Reproduce
Make a friend's only server, people join periodically. Friend says server can be seen through browser.
Status: Known Issue
We are aware of this issue and have it logged internally but either we do not have a fix ready yet or we are not planning on addressing the issue in the immediate future.