Hello,
i hope i am the only one that is having this issue, also a NOTE to ALL check if this issue is present in your servers aswell, so that other customer won't have access to mysql, filemanager to another cpanel. Hereby is my issue:
1. Create account with domain i.e: domainname.com with username i.e: domain (login to this user and create mysql database, and any file in filemanager/public_html)
2. Create similar account with domain i.e: domainnames.com with username i.e: domains (now login to this domain account go to mysql databases, and filemanager/public_html, you will be able to see and reach, mysql database, files that belongs to 1 account.