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/print.php?cal=Home,US+Holidays,Work &getdate=20061225%22%3E%3Cscript%3Ealert()%3C/script%3E&printview=day