Every onlinewallet can be dangerous, how we can see in the history.
There were "unicode tricks" and "DNS-attacks" to mention only two of them.
There are many attacks, which can lead to the complete loss of your coins.
The safest way is always to have your coins/tokens not on a exchange/online wallet but on a hardware wallet, like a ledger e.g.
Definitely, but the problem is that not all hardware wallets support all the coins. Some are still in process from a very long time. Exchanges and online wallets are never safe to hold coins/tokens.