On the dashboard I see “Webmin version 2.013 is now available, but you are running version 2.010”. But if I select “upgrade” I get “Failed to upgrade from www.webmin.com : HTTP/1.1 404 Not Found”
This is never enabled by default if Virtualmin is installed properly using virtualmin-install.sh script. How it was enabled, well good question but I think it should be asked to OP. Perhaps, Webmin was installed before running Virtualmin install script.
Although, it’s easy to make sure that this message is never displayed by adding to /etc/webmin/config file nowebminup=1 line.