As theymos said - security is never guaranteed and we agree that nothing is 100% safe. Each of us should have a way to avoid any losses in case of hacking and some small steps include not using inbox and outbox as a place to store some sensitive data.

However - instead of worrying about forums, I tend to worry about my own security from various cyber threats. Using strong passwords, enabling 2FA, not storing passwords online, not using the same password with various other accounts are some steps that might increase your own security. About forum security - I think that is the main task of the admin or the one who manages the forum, in this case theymos.