Does light exert a gravitational force?
No, a light photon or any photon cannot exert a gravitational force despite the magnitude of energy that is being propagated by the radiation. Radiation when intercepted delivers electromagnetic energy and therefore kinetic energy to the interceptor. The trouble in my opinion began with the ancient indecision concerning the fundamental dynamic nature of energy. The word mass was introduced to indicate the intrinsic kinetic and apparent static force essentially associated with the motion and inertial ability of that we call matter, and so we have the following various essential forms in which we find kinetic energy disguised by circumstances and time; rest mass, relativistic mass, gravitational mass, inertial mass, passive/active-mass. The dynamic nature of energy appearing in many diverse forms.