In the current version, the endpoints that list notifications, count them, and mark them read only check that someone is logged in — not specifically that they're an admin. Only the main notifications page itself checks for admin access and redirects other logged-in users away. A logged-in customer has no button or menu item anywhere that would call these endpoints, so this isn't reachable through normal use of the site, but it does mean those specific endpoints aren't hardened against a customer account calling them directly.