Two Critical Bitcoin Infrastructure Exploits Disclosed This Week: What Happened and What’s Next

Coldcard Mk3 Firmware Exploit

Root cause: A critical flaw in Coldcard firmware version 4.0.0, shipped in March 2021, caused the device to bypass its dedicated hardware randomness chip during seed generation. Instead of the expected 128+ bits of entropy, seeds were generated with only about 40 bits of effective security on Mk3 devices — making them trivially guessable by attackers who understood the weakness . The bug affected Mk2 and Mk3 devices running firmware versions 4.0.1 through 4.1.9, as well as Mk4, Mk5, and Q models prior to specific firmware updates .

Scale of losses: Over $116 million in Bitcoin was stolen from more than 5,200 addresses across four waves of thefts . On July 30 alone, attackers drained 1,082.65 BTC (worth approximately $70.2 million) from 1,196 wallets in roughly 41 minutes — just 30 hours before Coinkite, the company behind Coldcard, publicly disclosed the vulnerability . A second wave hit roughly 594 BTC from about 500 wallets, and subsequent waves brought the total losses to 1,816 BTC as identified by Galaxy Research .

Response: Coinkite released corrected firmware, but users must generate entirely new seeds and migrate their funds, as old seeds remain compromised . Former Binance CEO Changpeng Zhao warned that even cold storage is not fail-safe, emphasizing that this incident demonstrates no security measure is absolute .

BTCPay Server Lightning Credential Exploit

Root cause: A logic error in BTCPay Server's API authentication layer allowed unauthenticated remote attackers to access .macaroon credential files protecting LND Lightning nodes . These credentials are used for API authentication, and once obtained, they grant full control of the associated Lightning node .

What was stolen: Attackers emptied Lightning network channels on BTCPay Server instances, hitting confirmed victims including hardware wallet maker Foundation and Bitcoin zine Citadel21 . Standard BTCPay on-chain wallets were not affected .

Response: BTCPay Server released emergency version 2.4.2 on August 7, telling all operators to update immediately or take their servers offline . Critically, the patch stops new access but does not invalidate credentials already stolen — operators must also manually revoke and rotate LND macaroons and move funds from any BTCPay-generated on-chain hot wallet . BTCPay confirmed funds were stolen and said the attacks it reviewed targeted only files with the .macaroon extension .

Ecosystem Response: AI-Driven Security Audits

Bitcoin Red Team: A volunteer group led by developer Calle and AnchorWatch CEO Rob Hamilton, funded by OpenSats, launched a "large-scale ecosystem audit" using multiple AI models including Kimi K3, GPT Sol, Fable, Opus, and GLM5.2 .

Results: In roughly 30 hours, the team scanned 390 open-source Bitcoin repositories and filed 4,962 security findings, including 85 critical-severity and 635 high-severity vulnerabilities . The audit cost over $40,000 in AI compute . The team is responsibly disclosing vulnerabilities and plans to open-source its tooling to harden Bitcoin self-custody and broader crypto infrastructure .

Impact: The Coinkite bug has pushed open-source wallet developers toward AI-powered code audits as a standard practice . Coinkite itself noted it was likely that "someone used AI to review previous versions of our firmware" in its post-mortem .

Fund Migration Warnings and Onchain Activity

Bitcoin logged 2.27 million new wallets and 751,000 active wallets this week — its strongest onchain activity in months — as holders raced to move funds off Coldcard devices . Research firm K33 reported roughly 890,000 BTC moved over the prior seven days, the highest weekly active supply figure recorded in 2026 . Both Coinkite and BTCPay Server issued urgent public warnings that funds are at immediate risk and "attacks are ongoing" .

Bitcoin Price Impact

Bitcoin initially dropped nearly 3% to briefly touch below $62,000 when the Coldcard hack broke on July 31 . However, prices recovered quickly. By Monday August 3, BTC climbed past $64,000 — a 2.9% gain — as analysts noted the hack's limited market impact and the presence of eager buyers . As of August 8, Bitcoin remains near $64,000, but traders remain nervous, with Forbes reporting BTC is "braced for more critical exploits" amid the BTCPay news . The price has broadly held up despite back-to-back infrastructure shocks, reflecting market resilience.

Key Takeaways: Lessons for Self-Custody Security

The events of this week underscore several important lessons for Bitcoin holders and infrastructure operators:

• Firmware matters: Even hardware wallets can have critical firmware bugs. Regularly verify your firmware version and stay informed about security advisories.
• Seed generation is paramount: The Coldcard exploit worked because seeds were generated with predictable entropy. If your seed was created on vulnerable firmware, it is compromised regardless of what firmware you use now .
• AI cuts both ways: AI-assisted vulnerability discovery can be used by both attackers and defenders. The Bitcoin Red Team audit demonstrates the potential for AI to improve security at scale .
• Immediate action required: Both Coldcard and BTCPay Server users who may be affected must migrate funds and rotate credentials immediately, as exploitation is ongoing .