Quote from DonKee:
I would bet that ibkr is fairly hedged againt their own naked calls and naked put positions.
Their biggest losses will probably be from large clients and institutions that were sellers of bsc puts and are now long the stock on margin from much higher levels. Many of these clients will need to liquidate other positions from their portfolio to cover the margin calls.
This is the reason the fed is piling money into this. They are trying to avoid a massive liquidation of financial assets due to humongous margin calls.