This update is based on the latest release of Tor Browser, which was announced with this message:
The security flaw responsible for this urgent release is already actively exploited on Windows systems. Even though there is currently, to the best of our knowledge, no similar exploit for OS X or Linux users available the underlying bug affects those platforms as well. Thus we strongly recommend that all users apply the update to their Tor Browser immediately.
The release has been tagged on Github and you can find the signed, release APKs there. The update has also been pushed to Google Play, and should be rolling out over the next few hours. We will also be updating our F-Droid repo in the next 24 hours.
Finally, this marks the first time we have released an update of Orfox within 24 hours of a release of Tor Browser. We will continue to aim for this goal moving forward for both ongoing releases and critical updates.