We only support the latest production version, deployed to https://content.minetest.net. See the releases page.
We ask that you report vulnerabilities privately, by contacting rubenwardy, to give us time to fix them. You can do that by using one of the methods outlined in the following link:
Depending on severity, we will either create a private issue for the vulnerability and release a security update, or give you permission to file the issue publicly.
For more information on the justification of this policy, see Responsible Disclosure.