Abstract: A mirror assembly security system for a vehicle includes an exterior mirror assembly and a light module removably positioned within the exterior mirror housing. The light module is moisture impervious and includes an enclosure, a light-transmitting opening in the enclosure facing generally downwardly and/or rearwardly of the vehicle, a cover for the light-transmitting opening, and a light source in the enclosure radiating light through the light-transmitting opening. The light source may be received in a socket which removably engages another opening in the enclosure. In this manner, the light source may be replaced by removing the module from the exterior mirror housing, removing the socket from the enclosure and replacing the light source. The enclosure and mirror housing preferably are configured to self-retain the module in the exterior mirror moving with no, or fewer than one or two, separate fasteners.