Is it permissible for me to make modifications and program new websites to serve the forex trading business, after I became aware of the existence of Sharia prohibitions, and after my employer responded that there are no prohibitions in the matter?

We apologize for not browsing the forex owner's website, but the fatwa regarding the ruling on forex trading is clear. If the websites or new modifications do not differ from the prohibited forex, then it is not permissible for you to program or design websites for this purpose, due to the prohibition of aiding in sin. However, if the modifications remove the Sharia violations, then there is no objection to working with him.