PHP 'header()' HTTP Header Injection Vulnerability

An attacker can exploit this issue by enticing an unsuspecting user to follow a malicious URI. 

The following vulnerable code and example URI are available: 

<?php 

header('Location: '.$_GET['url']); 

print_r($_COOKIE); 

?> 

http://www.example.com/head1.php?url=http://example.com/head1.php%0DSet-Cookie:+NAME=foo