All perfect praise be to Allah The Lord of the Worlds and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
If the stock exchange company uses "Margin Trading" or "Forex", then we adopt the Fatwa issued by the International Islamic Fiqh Academy in its capacity as a scholarly-qualified Islamic body. However, if the trading is conducted by other means, then it is imperative that you (Asker) acquaint us with the terms and conditions of the contract concluded between the clients and the stock exchange company. This is in order for us to understand this issue in its totality to be able to deliver the correct legal ruling, Insh`Allah. And Allah Knows Best.