Worth noting it's different from August. That one drained Lightning nodes through leaked LND credentials, and the hot wallets were fine. This time it's the hot wallets, three days after 2.4.7 fixed 85 security issues. No word yet on which versions are hit, so down it goes.
Follow-up: BTCPay now says the attack vector hits 2.4.1 and older, and they have no credible reports of drains on 2.4.7. So the advice changed: update to 2.4.7, and only old instances should go offline right away. Still no word on how the admin logins happened.