Forex can't be easily manipulated since its value depends the economy of the country so technically, there are no whales there that tries to manipulate its value.
But we have seen so many cases where foreign currencies have also been manipulated, the latest being the Russian Rubble. Look up and see what happened to the Venezuelan national currency. The Government there even tried to change the denomination of the currency twice or thrice but nothing worked 
Regardless of who manipulates them, it's still called manipulation