source: https://www.securityfocus.com/bid/10605/info

Newsletter ZWS is reported prone to an administrative interface authentication bypass vulnerability. The vulnerability exists due to a design error in the implementation of the authentication system for the interface. The flaw allows a user to set their privileges through a URI parameter passed to the 'admin.php' script.

http://www.example.com/newsletter/admin.php?f=list_user&uname=test&ulevel=1