source: https://www.securityfocus.com/bid/18593/info

PHP Event Calendar is prone to an SQL-injection vulnerability. This issue is due to a failure in the application to properly sanitize user-supplied input before using it in SQL queries.

A successful exploit could allow an attacker to compromise the application, access or modify data, or exploit vulnerabilities in the underlying database implementation.

http://www.example.com/calendar.php?display=event&id=[SQL]