Background ---------- Firefox is very popular and secure web browser. Until now, it is used by milions of people and thousands of internet clubs. One of the great features of Firefox are extensions. You can use them to create things inside your browser which are beyond your imagination. But everything has an other side.. Overview -------- Writting a powerfull extension is extremely simple process. Extensions are allowed to do _everything_ with your browser: They can change the skin, block banners on pages or even create network connection and send data through it to the internet. The worst of all is that _anyone_, who has physical access to your computer, can install extensions into your browser _without_ your notification. As an example, I created a simple html form sniffer. You can download it here: http://azurit.gigahosting.cz/ffsniff/ It was tested only with Firefox 1.0.x and 1.5.x . FFsniFF is a simple Firefox extension, which transforms your browser into the html form sniffer. Everytime the user click on 'Submit' button, FFsniFF will try to find a non-blank password field in the form. If it's found, entire form (also with URL) is sent to the specified e-mail address. Solution -------- I think that the solution for this should be in the ability of locking the installation of extensions with a password. Every user will be able to read hash of the password (so the browser can verify it) and only system administrator will be allowed to change it (it can be stored for example in registers [Windows] or somewhere in /etc dir [Linux]). azurIt, azurIt@IRCnet, azurit (at) pobox (dot) sk