Is forex trading considered forbidden or permissible according to the Fatwas of various mujtahids, particularly Agha Sistani and Agha Khamenei?
Forex trading is permissible as far as it involves permissible trading and avoid Haraam dealings e.g. companies dealing with alcohol, gambling, usury, weapons to kill innocents, cheating etc.
You can easily contact the offices of any Marja' of Taqleed via email and seek their advice directly.
Wassalam.