glFusion 1.1.x/1.2.1 - 'users.php' SQL Injection

source: https://www.securityfocus.com/bid/46575/info

glFusion is prone to an SQL-injection vulnerability because it fails to sufficiently sanitize user-supplied data before using it in an SQL query.

Exploiting this issue could allow an attacker to compromise the application, access or modify data, or exploit latent vulnerabilities in the underlying database.

The vendor refutes this issue stating it can not be exploited as described. 

http://www.example.com/user.php?mode=1 and substring(version(),1,1)=4
http://www.example.com/user.php?mode=1 and substring(version(),1,1)=5