Starting with the release of proxysql-admin 2.0.15,  the proxysql-admin 2.x series can now encrypt the credentials needed to access proxysql and cluster nodes. This only applies to the proxysql-admin configuration, this does not change the ProxySQL config, so those credentials are still unencrypted. The credentials file is the unencrypted file containing the usernames, passwords, hostnames, [&]

https://www.percona.com/blog/2021/06/18/proxysql-admin-2-x-encryption-of-credential-information/