TorButton FAQ broken link
https://www.torproject.org/torbutton/torbutton-faq.html.en#extensionconflicts
"Like all vanilla third party proxy plugins, the main risks are plugin leakage" links to http://www.metasploit.com/research/projects/decloak/ which give a 404
Metasploit does show me anything for that. But there is http://www.decloak.net/ (it is contained in the TorBrowser Design=