The system runs the /usr/local/cpanel/bin/checkallsslcerts script during the nightly cPanel & WHM update (upcp) process. This script performs the following actions:
Installs a cPanel-signed hostname certificate on the server, if one does not exist.
Updates the SSL certificate for all cPanel & WHM services.
Issues a Comodo signed SSL certificate on any server with a self-signed, expired, or soon-to-expire certificate.