Once upon a time, the Tor Browser Bundle was an actual bundle. It included Firefox, the Tor daemon, and Torbutton, the extension to turn on and off the Tor mode in the browser.
From a technical point of view, Torbutton did not really go away. The visible button disappeared, but much of the related code remained.
Part of the state isolation code was not necessary anymore because Tor Browser always runs in private browsing mode or was dropped over the years thanks to Firefox improvements and the Tor Uplift initiative. However, the circuit display, the first-party domain circuit isolation, and other parts of the existing code were still needed. As a result, Torbutton continued to live for many years as a Tor Browser-only built-in extension on its separate repository and included in the browser with git submodules (even though the browser was non-functional without it). New patches and functionalities were written in the Firefox code that constitutes Tor Browser, and the Torbutton code was changed only to fix existing bugs or to keep it working in new versions of Firefox. … [Leggi il resto]