This is how XF deals with members URL's. And @Mike or @Chris D or @Kier can confirm this.How can this not be a bug?
Just copy this link and change the number and it will take your to the profile of the user in that number.
for example I change to your number (3084) and it will take me to your profile
This is an exploite that does not exist in other forums.
Actually, it's pretty much how every single forum software works, ever.This is an exploite that does not exist in other forums.