Exchange 2013 Public Folders implicit permissions

Hi,

 I have fresh Exchange 2013 without SP1. I am testing PF but I discovered strange thing. I create PF with permissions only for two users but the third user can access them and edit without problems, I also trid to modify root folder permissions but no change. Are there any implicit permissions that allow all users to access anything so they have to denied access explicitly or can I change these implicit permissions? Or am I doing something wrong? Thank you.

Pete

sfs