a) I'm not sure how they'll react (will they claim I'm trying to extort them?)
b) there's never any clear way to contact a company beyond calling/emailing 'customer support'.
Occasionally I've tried to poke around my linkedin network to see if I had a connection at company X to reach out to their dev team and notify them of something, but I've never been successful that way (but also haven't pushed the issue much).