source: https://www.securityfocus.com/bid/21792/info
  
PHP icalendar is prone to multiple cross-site scripting vulnerabilities because the application fails to properly sanitize user-supplied input. 
  
An attacker may leverage these issues to have arbitrary script code execute in the browser of an unsuspecting user. This may help the attacker steal cookie-based authentication credentials and launch other attacks.
  
http://www.example.com/phpicalendar/year.php?cal=all_calendars_combined971 &getdate=20061225"><script>alert()</script>