pgAdmin 4's materialized view refresh passed the target database's name to psql's --dbname argument unchanged. libpq treats a --dbname value containing "=" (or a postgresql:// URI) as a full connection string, whose keywords override the host, port and other settings pgAdmin had supplied. A database whose name is such a string, which any role with CREATEDB can create, therefore redirected the psql process pgAdmin starts for the refresh to a host and port of the creator's choosing, and the connecting user's saved server password was presented to that endpoint. It also let the pgAdmin host be made to open connections to arbitrary addresses. The same weakness was fixed for Backup, Restore, Main