The latest Version (tag with highest number) is supported on a per best effort basis. This is a hobby project.
This library does not have a lot of code and is thoroughly tested. Vulnerabilities will most likely surface in OptParse, which is wrapped by this library. So keep an eye on updates over there.
You may report everything as an issue here, as there are not many users yet and the vuln most probably need user interaction. If not tell me in an issue and I can see what I can do :)