Basically we don't know the risk in every site if you invest money in a site first is you don't know if the site was trusted there are site that can give you small profit but many site are just scamming people who invested.
Yes it true, we cannot tell how much risk it is. It depends on the site you use some are scam and others are legit. My advice us find a reliable site and that's it when you find it, it will be less risk more profits. It's the site and people you invest in are risky, the coins are not especially bitcoins that rises its value from time to time.