IgorG, in http://kb.odin.com/en/123160 there is no information about securing the Plesk Web Server itself. Why?
I patched it by adding
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
to the /etc/sw-cp-server/conf.d/plesk.conf file and restarting the Plesk Web Server afterwards:
/etc/init.d/sw-cp-server...