Tether claims that most of their tokens are backed up with real assets (either US Dollar or other assets that are denominated in USD).
This alone is already pointing out how flawed Tether is. They started by claiming that EVERY token is backed by the fiat currency it is pegged to, and now they changed their terms to make it appear that they never claimed to do.
Since most of these assets are stored in the form of fiat currency (that too in physical form) I don't understand how can some hacker exploit the situation. And in case some hacker steals the tokens, then they can just reverse the transaction just like what ETH did after the DAO robbery.
That doesn't work here. It would require you to roll back the Bitcoin blockchain.... Good luck with that. Tether also can't freeze or reverse your transactions. In other words, tokens that are stolen are stolen for ever.
What you can do is blacklist the address of the hacker and hope the rest of the ecosystem follows that, but even this measure hasn't always been effective looking back at how hackers have successfully spent or sold their coins.