Directory traversal vulnerability in index.php in PHP Doc System 1.5.1 and earlier allows remote attackers to access or include arbitrary files via a .. (dot dot) in the show parameter.
http://www.vupen.com/english/advisories/2005/2622
http://www.securityfocus.com/bid/15611
http://secunia.com/advisories/17745
http://pridels0.blogspot.com/2005/11/php-doc-system-151-local-file.html