What a Week | THE BITCOIN BRIEF 86

A bi-weekly news show informing you on the latest in Bitcoin, privacy and open source tech hosted by Ungovernables, Max and Q.

THIS IS THE TWEET Q WANTS YOU TO SEE: https://x.com/justh0dl/status/2086202393998291138

AOB What a fucking week KeyOS v1.3.1 now publicly available Something exciting to share on Friday's FTF (delayed by 2 weeks) NEWS

The Coldcard entropy catastrophe

Sources: Coinkite technical backgrounder / The Rage, L0la L33tz / TRM Labs / coldcard.rip / cktripwire.com / Bitcoin Magazine victim survey

EXPLAINER The largest self-custody theft on record, and it traces back to a single wrong conditional. In March 2021 a build guard checked whether Coldcard's hardware random number generator was defined rather than whether it was enabled, so seed generation silently fell back to a deterministic software PRNG. Every seed made on an affected device from that point carried roughly 40 bits of entropy on Mk2 and Mk3, and about 72 on Mk4, Mk5 and Q, instead of the intended 128. That is guessable. Someone did the maths offline, derived the addresses, checked them against the public chain, and swept everything with a balance. Somewhere between 1,400 and 1,800 bitcoin gone, depending on whose forensics you trust, with a median victim loss of one BTC. The part people keep missing: updating the firmware does not fix an existing seed. A weak seed is weak forever.

ACTION FOR LISTENERS Move funds to a brand new seed BEFORE upgrading firmware (Lopp's guidance, on reports of update problems). Use high fees. If you see your own coins in the mempool, the attacker opted into RBF and you can outbid them. Window is minutes. Multisig users: consider a private mempool like Marathon's Slipstream. Keep the device; the UID may prove ownership in any recovery process. Updating does NOT fix an existing seed. A weak seed is weak forever. You are exempt only if you added 50+ fair independent private dice rolls, or used a strong unique BIP39 passphrase stored separately.

BTCPay Server: unauthenticated LND macaroon theft, actively exploited

Sources: BTCPay security advisory / v2.4.2 release / CoinDesk / TFTC CRITICAL FRAMING NOTE: this is ONE story, not two. The "BTCPay bug" and the "LND credential exploit" are the same event. The vulnerability is the macaroon leak. The Aug 8-9 wave of coverage is follow-up hardening, not a new incident. Do not present them separately. REMEDIATION (updating alone is NOT enough) Update to v2.4.2. Verify "2.4.2" in the footer. Update NBXplorer to 2.6.10+. Revoke and regenerate LND macaroons. Updating stops new theft but does nothing about already-stolen credentials. Deleting files is insufficient; the macaroon root signing key must be destroyed at node level. v2.4.2 does this automatically for standard Docker deployments. Custom reverse proxies, separate Tor services or port forwarding must rotate manually. Move funds out of any BTCPay-generated on-chain hot wallet and recreate it. Update LND to 0.21.1. Audit for unrecognised channel closures, unknown peers, unexplained balance changes. SIDE EFFECT WORTH FLAGGING: v2.4.2 removes public LND API access on Docker deployments, which breaks remote wallet connections such as Zeus connecting to your own BTCPay node. Intentional, no restoration timeline published. BREAKING CHANGE: Greenfield Basic authentication disabled by default five minutes after account creation (#7492). BTCPay: "We are not aware of any user impacted by this breaking change, as API Keys authentication is generally used."

Boltz suspends all swaps indefinitely Sources: Boltz statement / canary.boltz.exchange / The Defiant / TFTC / Bull Bitcoin statement CORRECTION TO THE COMMON FRAMING: Boltz has not shut down. It suspended swap services indefinitely. And the canary sequence runs the opposite way to the rumour: lapsed → suspended → renewed clean.

The Bitcoin Red Team Sources: Calle and Rob Hamilton on Nostr/X / Bitcoin Magazine / CoinDesk / TFTC / OpenSats Red Team Fund SUMMARY This is the story t