Luckily for them, they were able to pause the contract before anyone exploited it in ways that were not so easily rectified. The ability to receive $1 trillion in USN out of $1 could have easily been used to drain the USN/USDT liquidity pool.
A user tried twice to swap $5 of the USN stablecoin for Tether on the Decentral Bank platform. Both times, the transaction failed due to a bug that prevented users who didn't already hold Tether from swapping other currencies for Tether. The refund mechanism also had a bug, and both times the system failed to process the transaction, the user ended up being refunded $5 trillion instead of $5.