Over a thousand bitcoins are believed to have been stolen so far in a hack that started to be discussed on social media in the afternoon of July 30th. Coinkite, one of the most reputable hardware wallet manufacturers, was revealed to have a critical bug in the way it generated secure private keys for its Bitcoin hardware wallets. Industry experts believe AI was used in the breach.
Coldcard MK3 devices with firmware version 4.0.1 (March 2021) through 4.1.9 are the worst affected. 12- or 24-word seeds generated by the device that did not include user-generated dice rolls or a BIP 39 extra passphrase are vulnerable.
Users who fit this category, who have bitcoins in an MK3 Coldcard and did not use the dice roll feature for extra entropy or the extra passphrase, should consider themselves at risk and move their coins as soon as possible from the wallets. Bitcoin Magazine technical writer Shinobi has published a guide on the topic, and Coinkite has also published a guide and advisory.
The vulnerability was a specific line of code in the firmware, a low-level software codebase that controls the hardware. This firmware appears to be upgradable. The Coinkite advisory was updated this morning, advising users to upgrade device firmware for all three chips, MK3, MK4 and MK5 devices, including the Coldcard Q:
