source: https://www.securityfocus.com/bid/14763/info

phpCommunityCalendar is prone to multiple SQL injection vulnerabilities. These issues are due to a lack of proper sanitization of user-supplied input before being used in SQL queries.

Successful exploitation could result in a compromise of the application, disclosure or modification of data, or may permit an attacker to exploit vulnerabilities in the underlying database implementation. 

http://www.example.com/[path]/webadmin/login.php and use this:

login: ' or isnull(1/0) /*
password: [nothing here]