What is the ruling on the commission taken by an affiliate marketer from a foreign car rental company, in the event that the customer pays an additional amount—optional, not compulsory—in exchange for activating the collision damage waiver service on the rented car?

If the fee is known, there is no problem. However, if it is unknown, it is not permissible for the commission to be a percentage of the profit, according to the majority of scholars, due to the uncertainty. The Hanbalis, however, permit ju'alah (a promised reward for a specific act) even if the reward is unknown, provided that it does not prevent delivery, such as "whoever returns my lost item shall have one-third of it." What the lessee pays to the company to activate collision damage protection is not relevant to the questioner.