<span class="application">[Tor Browser](https://www.torproject.org)</span> is a web browser based on [Mozilla Firefox](https://www.mozilla.org/firefox/) but configured to protect your privacy.
Security vulnerabilities in JavaScript have been used to [deanonymize Tor Browser in the past](https://arstechnica.com/information-technology/2013/08/attackers-wield-firefox-exploit-to-uncloak-anonymous-tor-users/).
For example, here is how the browser looks when we try to log in to an email account at [riseup.net](https://riseup.net/), using their [webmail interface](https://mail.riseup.net/):
Notice the padlock icon on the left of the address bar saying "mail.riseup.net".Notice also the address beginning with "https://" (instead of "http://"). These are the indicators that an encrypted connection using [[!wikipedia HTTPS]] is being used.
When you are sending or retrieving sensitive information (like passwords), you should try to only use services providing HTTPS. Otherwise, it is very easy for an eavesdropper to steal whatever information you are sending, or to modify the content of a page on its way to your browser.