There was a short spike of CHFPLN on Forex few years ago: exchange rate went from less than 4.00 PLN to 5.50 PLN, because of Swiss central bank decision to not stabilize it anymore. Some people made a lot of money (or so they thought). Few days later the broker declared that spike "a technical glitch" and they cancelled all the trades.
The moral of the story is: your exchange will always find a way to screw you.
The moral of the story is: your exchange will always find a way to screw you.