Ads by Coupon Addon is classified as an adware program, as it gets installed on the targeted computer without any manual interference. It spreads through different location and places so it may also get downloaded with some fake updates of freeware and shareware that you do. Being an ad-supported program, Ads by Coupon Addon may not be dangerous as it looks, but...
Remove Ads by Coupon Addon: Know How To Uninstall Ads by Coupon Addon