We’d need more context. Something will have triggered that. For example your bug report where the register overlay loads the forum list - testing that will involve you being in inconsistent login states across two open tabs and that would trigger that.
It generally indicates you’re logged in or out on one tab and then either logged in as a different user or logged out or in on another.
If you can provide context as to what you were doing it will help, otherwise it’s likely just doing what it was designed to do.