Update your plugins. Your "secure" server is likely a house of cards. To Ethical Hackers: If you find a bypass, report it to the developers on GitHub—don't sell it to griefers.
Understanding Minecraft AuthMe Bypass: Vulnerabilities and Prevention Minecraft Authme Bypass
A standard exploit flow looks like this (simplified): Update your plugins
: Use iptables or UFW to ensure that backend servers only accept connections from the proxy's IP address. Minecraft Authme Bypass