Directory traversal vulnerability in Jim Hu and Chad Little PHP iCalendar 2.21 and earlier allows remote attackers to include and execute arbitrary local files via directory traversal sequences and a NUL (%00) character in the phpicalendar[cookie_language] and phpicalendar[cookie_style] cookies, as demonstrated by injecting PHP sequences into an Apache access_log file, which is then included by day.php.
https://www.exploit-db.com/exploits/1585
http://www.vupen.com/english/advisories/2006/1019