XSS by uploading/including a SWF file

As you may already know, it is possible to make a website vulnerable to XSS if you can upload/include a SWF file into that website. I am going to represent this SWF file that you can use in your PoCs.

This method is based on [1] and [2], and it has been tested in Google Chrome, Mozilla Firefox, IE9/8; there should not be any problem with other browsers either.

Note: IE has a protection to make the “document” object inaccessible when you open a SWF directly in a browser. I have bypassed IE8 protection by using a simple redirection in Javascript. I have also found a noisy way to bypass IE9 protection by opening a new window (you may be able to do it in a less noisy way – please leave your comments if you know any other bypass method).

Here is the actionscript code:

Compiled file is accessible via: http://0me.me/demo/xss/xssproject.swf

Examples:

Browsers other than IE: http://0me.me/demo/xss/xssproject.swf?js=alert(document.domain);

IE8: http://0me.me/demo/xss/xssproject.swf?js=try{alert(document.domain)}catch(e){ window.open(‘?js=history.go(-1)’,’_self’);}

IE9: http://0me.me/demo/xss/xssproject.swf?js=w=window.open(‘invalidfileinvalidfileinvalidfile’,’target’);setTimeout(‘alert(w.document.location);w.close();’,1);

References:

[1] The other reason to beware ExternalInterface.call() (URL: http://lcamtuf.blogspot.co.uk/2011/03/other-reason-to-beware-of.html)

[2] Flash ExternalInterface.call() JavaScript Injection – can make the websites vulnerable to XSS (URL: https://soroush.me/blog/2011/03/flash-externalinterface-call-javascript-injection-%E2%80%93-can-make-the-websites-vulnerable-to-xss/)