What is the ruling on the aforementioned transaction, which involves marketing goods for others online in exchange for profit, with the marketer bearing the costs of returning the goods should the customer refuse to receive them, and how can this transaction be corrected if it is not permissible?

It is permissible to promote goods for a known fee, and for the fee to be the amount exceeding a certain price. This is permissible according to Ahmad and Ishaq, who likened it to Mudarabah (definition) (profit-sharing). Al-Bukhari narrated from Ibn Abbas, who said: "There is no harm in one saying: 'Sell this garment, and whatever it exceeds such-and-such, that is yours.'" The agent is entrusted and is not liable except in cases of transgression or negligence. Therefore, if the marketer fulfills their duty and then a loss occurs or the merchandise is returned, it is not permissible to charge them anything, such as shipping fees, and stipulating that upon them is invalid.