Always use the latest version of the project (including patch version). Older versions are not being patched as the upgrade process is straightforward.
In case you find a vulnerability, please report it via issue or email as soon as possible.
You can directly propose a solution using a Pull Request (see CONTRIBUTING file).
In case you need to provide also sensitive information related to a vulnerability, please indicate that in the issue and we will let you know how to securely provide us such information.