Is working in a financial brokerage firm, mediating between clients and the stock market for a fixed monthly salary, impermissible (haram) or permissible (halal)?

If the buying and selling of shares are subject to the Shariah controls mentioned in Fatwas no. 31570 and 30649, then there is no objection to acting as an intermediary between the stock exchange and those wishing to buy or sell shares. Otherwise, it is not permissible, because it would then be considered cooperation in sin and aggression. Please refer to Fatwa no. 3977.