Hello,
sometimes I see coins on coinmarketcap which shows extreme gains,
but when I look at the exchanges, the price is much lower.
For example 6 $ on Coinmarketcap and 2 $ on an exchange.
How is that possible? Is this a bug or manipulation?
No manipulation is going on at Coinmarketcap. They act like directory of coins and tokens. They post whatever is the status or current price of coins and tokens. However the price that you see there is based on the exchanges where the coins and tokens is listed. Not sure if its the average of the coins or token if it is listed in multiple sites.