6 June 2016, the Tor Project announced a hardened version of Tor Browser: 6.5a1-hardened.
Here some links:
- Download page for hardened builds (only avaible for Linux at this time).
- Distribution directory.
- Official announcement by the Tor Project.
- Firefox security updates
In order to prevent intelligence agencies to de-anonymize Tor users using exploits, Tor hardened version includes Selfrando.
Selfrando is a load-time randomization software that aims to improve security over standard address space layout randomization (ASLR) techniques.
Selfrando doesn't overhead performance very much (less than 1%) and doesn't need too many chnages in the existing Tor Browser code.
For more details, researcehrs from University of California published a report entitled Selfrando: Securing the Tor Browser against De-anonymization Exploits.