source: http://www.securityfocus.com/bid/66923/info

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

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

Jigowatt PHP Event Calendar 2.16b is vulnerable; other versions may also be affected. 

http://www.example.com/code/calendar/day_view.php?day=23&month=4&year=[SQL injection]