A cap for a container closure or closure plug is disclosed. The cap includes a cap top having a top surface and a bottom surface, and an attachment ring extending axially downward from the bottom surface of the cap top under a central portion of the cap top. The attachment ring is securingly engageable with a container closure or closure plug. The attachment ring includes a cam surface extending radially outward from the attachment ring, where the cam surface is configured to deflect the attachment ring radially inward upon engagement of the attachment ring with the container closure or closure plug. The cap top and the attachment ring are connected by at least one frangible connection and at least one permanent connection, where the at least one permanent connection is configured to retain the cap top and the attachment ring upon breaking of the at least one frangible connection.