What is the ruling on money I obtained from an investment if it becomes apparent that the broker lent the money with interest without my knowledge, and must I demand the excess amount the broker obtained to dispose of it as well?

This issue is not without two possibilities: Either the agent paid the money to a third party on the basis of usury, and in this case, the agent has committed a grave sin by betraying his principal, and he must return the usury if possible, otherwise dispose of it by spending it on the welfare of Muslims. The other possibility is that the agent paid the money to a third party for investment. Here, it is considered whether the investment is lawful or not. If it is a legitimate Mudarabah (partnership) without guaranteeing the principal, then it is permissible. However, if the principal is guaranteed or an additional percentage is added to it, then the Mudarabah is invalid, and the investor is only entitled to a fair wage, and the profit belongs to the owner of the principal.