insecure defaults with postgres public schema?
You can revoke the public schema "create" permission in the template1 database, and this will be propagated to any newly-created database by default: databases are created by copying template1 (or some other database marked as a template, but template1 is the default).
Actually, you might want to simply drop the public schema altogether in this situation, and delegate the job if creating it (if desired) to the database owner.
I used this article to advantage when I needed to a secure database: