Is taking commission for marketing products online permissible or forbidden, knowing that the one who gave me the job takes a commission from me on every product?

It is permissible to market products in exchange for a known commission, as this falls under permissible brokerage. If someone directed you to a job or mediated for you, they are entitled to a one-time commission for the referral or for securing you the job. However, they are not entitled to a commission on every product you market, because profit is only deserved through capital, work, or guarantee. There is no work here after the initial referral. Therefore, whoever guarantees something, its yield is theirs. It is not appropriate for one person to say to another: "Dispose of your money on the condition that the profit is mine," or "on the condition that the profit is between us." This is absurd, and all profit belongs to the owner of the capital.