Wintermute hasn't disclosed more about the attack, but it's possible that the hacker may have exploited the vulnerability in the vanity wallet address generator Profanity, which was disclosed five days prior. The crypto asset vault admin had a wallet address prefixed with
0x0000000, a vanity address that would have been susceptible to attack if it was created using the Profanity tool.
This is the second incident involving Wintermute in the past few months. In June, the group provided the wrong wallet address to the Optimism project, and Optimism sent 20 million OP tokens to a non-existent address. Another person noticed the error before they did and was able to take the tokens. They ultimately returned 17 million of the tokens to Wintermute, keeping the rest as a "bounty". $OP have been trading at around $1 as of mid-September.