Is it Islamically permissible to participate in global stock exchange currency trading companies that guarantee a profit margin ranging from 7% to 12% on capital and a loss not exceeding 10%? And is there any usury (riba) in that?

If the determination of 7% or 12% is from the anticipated profit, then it is permissible, and it is a Mudarabah (profit-sharing partnership). However, if this percentage is guaranteed from the capital itself, then it is impermissible and constitutes usury (riba). Specifying a percentage for loss is also impermissible because it implies guaranteeing a portion of the capital.