Liquid Drained of 4,000 BTC, Self-Styled White Hats Hand Back 3,400 a Day Later

The biggest crypto heist of 2026 so far needed no stolen keys and no phishing, just one flawed caching routine and 36 minutes.

Three key facts

On September 6, roughly 4,000 BTC (about $319 million) left Liquid's federation wallet. According to TRM Labs, the attackers minted around 4,000 L-BTC with no real bitcoin behind them, requested a withdrawal via SideSwap, and the 11-of-15 multisig federation dutifully paid out real BTC. Mint to payout took 36 minutes. Blockstream says no signing key was compromised.

The flaw sat in the caching logic of Elements, Liquid's open-source node software. Range-proof verification is expensive, so Elements caches the results. The attackers abused that cache so an invalid output was waved through as already verified, creating unbacked L-BTC.

On September 7, the attackers sent 3,400 BTC (about $270 million, or 85%) back to the federation wallet. In an on-chain message they called themselves white-hat researchers and asked Blockstream to patch the bug first. About 598.5 BTC, worth roughly $47 million, is still outstanding, and Liquid's peg and L-BTC trading remain paused.

WangDou's Take

The punchline: Liquid's whole pitch is that a federated multisig is safer. Fifteen signers, eleven required signatures, zero keys lost, and the vault still got emptied, because the signers sign and nobody questions the software when it says "already checked." Security rarely fails at the number of locks; it fails at the guard who trusts the pass. As for "white hat," taking 4,000 coins and keeping $47 million after negotiations is not charity. A bank robber who returns 80% of the cash is not a temporary custodian. The bigger lesson for every bitcoin sidechain and L2 selling "mainchain-grade security": your real security ceiling is the most boring cache function in a few hundred thousand lines of code.

Source: TRM Labs · CoinDesk · The Hacker News