Since this software is still considered beta/WIP support is always only given for the latest version. Security patches are only available for the latest version and not back-ported to older versions.
For general security vulnerabilities you're welcome to open a GitHub issues or contribute a fix. If you feel the vulnerability should not be disclosed you can open a generic issue on GitHub and email to the details to ob92oy0sl@mozmail.com which is monitored by the maintainer.