source: https://www.securityfocus.com/bid/12893/info

Topic Calendar is reportedly affected by a cross-site scripting vulnerability. This issue is due to a failure in the application to properly sanitize user-supplied input.

An attacker may leverage this issue to have arbitrary script code executed in the browser of an unsuspecting user. This may facilitate the theft of cookie-based authentication credentials as well as other attacks.

http://www.example.com/phpbb/calendar_scheduler.php?start=%22%3E%3Cscript%3Ealert(document.cookie)%3C/script%3E