Tor Browser 6.5a6 is now available from the Tor Browser Project page and also from our distribution directory.

This release features important security updates to Firefox. Other components got an update as well: Tor to 0.2.9.6-rc and HTTPS-Everywhere to 5.2.8.

With this release we made progress in both the usability and security area. In the former we fixed the broken preferences pane in non-en-US bundles and moved to pt-BR bundles for Portuguese as it turns out that all our translations for Portuguese are containing Brazilian language strings. We added links to the Tor Browser Manual, an effort led by the community team to make help easier available for our users in case of problems.

On the security side we are proud to announce the first fruits of our sandboxing efforts.

On Linux the Tor Browser sandbox is centered around Linux namespaces along with seccomp-bpf, and attempts to reduce the attack surface available to adversaries to prevent exploits from succeeding, and to limit the capabilities of an attacker in the event that they do manage to compromise either the tor client instance or the browser itself. This is done by creating lightweight namespace based containers in which the Tor Browser components are run, with various restrictions imposed by the operating system. For example, the container that the browser runs in does not have an IP address to leak, or a connection to the external network except via Tor.

It is made available to end users as a separate downloadable binary, sandboxed-tor-browser , that manages installing and updating Tor Browser, configuring Tor and the sandbox, and running the actual sandboxed Tor Browser. Having bubblewrap installed is required for this to work. Additional documentation about the implementation, known issues, and frequently asked questions is available at our wiki.

We have also made some progress with sandboxing on macOS. Building on the work done in the past by IronFox and similar projects, we have created sandbox profiles for the Tor daemon and for Tor Browser itself. These profiles, along with some command line scripts that use Apple's sandbox-exec command to start Tor and Tor Browser, are included in our Tor Browser 6.5a6 OSX packages. At this time we are asking advanced users to use the OSX sandbox profiles on an experimental basis and give us feedback on any problems that they encounter. In the future, we hope to create software for macOS that is similar to the Linux Tor Browser sandbox.

Besides work on sandboxing this release features our first step in exploring options to harden the memory allocator. We have enabled jemalloc4 on Linux bundles and abort on redzone corruption. We are here especially interested in performance and stability related feedback.

Here is the full changelog since 6.5a5: