Help. How did this hack happen? I'm ready to pay for a private consultation

Thank you!
I searched inside simple login and i cannot find that breach alert anywhere, do you have a screenshot?

I forgot to mention that if you have a domain name, then you can have custom email aliases based on your domain or subdomain.
When you delete them from simplelogin you can add them back if you want, unlike aliases given by simplelogin domains where if you delete an alias it’s gone forever (for security).