Because a third party app on Windows can edit the Firefox preferences file to set the opt-out preference and then install its unsigned malware&#x2F;spying&#x2F;ad-injecting extension and it&#x27;ll be loaded the next time Firefox starts up with no warning to the user.<p>This is why Chrome hashes its settings files on Windows so that when any 3rd party app tries to mess with it, it wipes all extensions and extension settings and resets the homepage and search engine to the defaults.  Unfortunately this also means that you can&#x27;t move your Chrome settings to another PC as they&#x27;ll all get reset.  You have to sync to Google to ensure all your settings aren&#x27;t wiped by a badware app or a corrupt byte in the Chrome settings file.