Coldcard Mk3 Users Warned to Move Bitcoin Amid Coordinated Sweep

Coldcard users are being warned to move their Bitcoin from wallets whose seed phrases were generated on affected firmware. The Canadian hardware maker Coinkite issued a warning after investigating a coordinated sweep of $38.2 million worth of BTC, worth about 594 BTC.

The notice affects seeds created on firmware versions 4.0.1 through 5.0.3 and recommends generating a new seed on an unaffected device or using a strong BIP-39 passphrase as a temporary measure for those whose Mk3 is their only option.

No public evidence links the issue directly to the sweep, but Coinkite's advisory gives users more detailed migration options. They suggest verifying the backup and receiving address, sending a small test transaction, and moving the remaining balance after confirmation.