Bitcoin hardware wallet manufacturer Coldcard's official X account was compromised on October 11, 2026. Attackers published a fake notice about a "critical firmware vulnerability" for Mk4, Mk5, and Q models, urging users to move funds via a phishing website. The scam leveraged user anxiety from a July 2026 linker error crisis that led to approximately $100-$130 million in losses due to weak entropy. Coldcard stated it found no evidence of a breach in its own systems, with credentials and offline 2FA remaining secure, and has contacted X support for an urgent investigation.