From New Release: Tor Browser 13.0.12 | The Tor Project
Removal of automatic .onion site prioritization
The Tor Project has recently been notified of a potential fingerprinting vulnerability with automatic Onion-Location redirects. In an abundance of caution, we have removed the ‘prioritize .onion sites when known’ option from Tor Browser. We are looking further into this issue and will provide timely updates as more research and additional recommendations become available.
- Bug tor-browser#42444: Remove the “Prioritize .onion sites when known” option
Bug seems to be confidential…