Extract from article:

The estimated cost of the attack was about 285 USD. We broke 762 unique wallets. All of these had a zero balance. Interestingly enough, we could break all these wallets, not because of a linear or quadratic recurrence but because there was at least one repeated nonce in the signatures. So, it looks like the common mishap of ECDSA implementations using a repeated nonce was the cause of trouble.