Cybersecurity experts have warned that hackers are targeting Coldcard Bitcoin hardware wallets. The attack is a supply chain compromise. Attackers tamper with the devices before they reach buyers. Hardware wallets are used to store cryptocurrency offline. They are considered safer than online storage. A compromised device can leak secret keys or show wrong addresses. Buyers are told to check packaging seals and verify firmware on arrival. The warning follows reports of tampered units in circulation. Coldcard is one of the most popular Bitcoin-only hardware wallets. Security researchers say supply chain attacks are hard to detect. Users should buy only from official sellers. Anyone who bought a Coldcard recently should verify its integrity before moving large amounts. Researchers say buyers should check packaging seals and verify firmware on arrival. Coldcard is among the most popular Bitcoin-only hardware wallets. Supply chain attacks are hard to detect. Users should buy only from official sellers.