Torbutton is the component in Tor Browser that takes care of application-level security and privacy concerns in Firefox. To keep you safe, Torbutton disables many types of active content.

Now that the Tor Browser includes a patched version of Firefox, and because we don't have enough developer resources to keep up with the accelerated Firefox release schedule, the toggle model of Torbutton is no longer supported. Users should be using Tor Browser, not installing Torbutton themselves.

Developer Documentation: Torbutton Design Document and Slides (Not actively updated)
Source: You can browse the repository or simply unzip the xpi.
Bug Reports: Torproject Bug Tracker
Documents: [ changelog | license | credits ]