It's the way cwp staff will force you to upgrade.
The problem is that the upgrade is not possible without having serious issues(search the forum and you will see).
To avoid the message and restore the login page, login to your ssh shell and do as it follows:
cd /usr/local/cwpsrv/htdocs/
rm -rf admin
mv admin_disabled admin
now the login page is back, but soon it will be replaced again with the error message and you will be forced to follow the procedure each time you want the login page back, so to keep it alive, you have to issue the following command:
cd /usr/local/cwpsrv/htdocs/
chattr +a admin
now the admin folder cannot be modified or deleted even by root user and the login page will stay on line.
to unprotect the admin folder, you'll have to issue the following command:
chattr -a admin
This is a temporary solution, also if you want to keep using cwp in the future, the only option is to contact support and pay cwp staff for the upgrade.
Also check on line exploit databases like
https://0day.today/search?search_request=centos+web+panelto be sure that your version is safe.