Nearly 4,000 bitcoin worth roughly $320 million walked out of Blockstream's Liquid Network federation wallet on September 6, after a software bug in the Elements codebase allowed an abnormal peg-out to pass through the sidechain's standard authorization process. The funds remain in the hands of actors who identify themselves as "white hats" and say they will return the bitcoin — but only after every affected node is patched.
How the exploit unfolded
The sequence began at approximately 14:05 UTC on September 6, when a customer submitted 4,000 L-BTC to SideSwap, a decentralized exchange built on Liquid, for conversion back to bitcoin on the main chain. SideSwap said the request passed its normal authorization process, which prompted Liquid's federation — a 11-of-15 multisig body — to approve the peg-out. Twenty-three minutes later, at 14:28 UTC, 3,996.01834922 BTC left the federation's multisig reserves through a Peg-out Authorization Key, according to CryptoBriefing.
The federation's proof-of-reserves page subsequently showed holdings of approximately 197 BTC, down from more than 4,200 BTC before the event. That represents a 95 percent decline in a single transaction. Both Blockstream and SideSwap attributed the withdrawal to a software flaw in Elements, the open-source codebase that powers Liquid's infrastructure, rather than to compromised signing credentials.
A public negotiation on-chain
What followed was unusual even by crypto standards. The actors controlling the funds broadcast OP_RETURN messages — small data payloads permanently recorded on the Bitcoin blockchain — addressing Blockstream directly. One message read: "we are whitehats. contact us on chain." Galaxy Digital head of research Alex Thorn said a Blockstream-linked address responded with a request to contact security@blockstream.com, while the holder later offered a Signal handle for further communication.
The negotiation continued across multiple transactions. According to DailyCoin, which tracked the on-chain messages, the holder proposed sending "most" of the bitcoin back to the federation. Blockstream's reply, delivered through a subsequent OP_RETURN spend, was that the vulnerability must first be fixed and every node patched before funds can safely be returned. "Please fix the bug first," the message stated. "Make sure every node is patched. Then we will transfer the money back safely after confirming the fix."
As of September 7, zero BTC has been returned.
What the bug reveals about federated sidechains
Liquid operates as a federated sidechain of Bitcoin, founded by Adam Back's Blockstream. It issues a variety of assets including L-BTC, which it backs with BTC held in a large multisig wallet on the Bitcoin main chain. The design requires 11 of 15 designated functionaries to sign off on peg-outs, and a Peg-out Authorization Key system restricts payments to approved wallets. The Elements bug apparently circumvented both layers of protection by allowing invalid L-BTC to enter a valid peg-out flow.
The incident does not appear to have affected non-BTC assets on the Liquid Network. Liquid's official account said on X that other issued assets, including USDT and tokenized securities, remain unaffected because the flaw was specific to the BTC peg-out mechanism.
Exchanges were instructed to pause L-BTC deposits and withdrawals, and Liquid disabled its bridge nodes, freezing the connection between the sidechain and Bitcoin's mainnet. Users holding L-BTC now face an uncertain redemption path, with the underlying bitcoin reserves depleted and no timeline for a fix.
Parallels and open questions
The episode echoes the 2024 Ronin Bridge incident, when a white-hat MEV searcher exploited a vulnerability and withdrew roughly 4,000 ETH and $2 million in USDC. Ronin resolved that case in about 80 minutes, returning the funds after a $500,000 bounty. The Liquid situation is nearly 27 times larger and the funds remain in the alleged white hat's custody, with a condition attached that Blockstream has not yet met.
Blockstream had not issued a public statement at the time of writing, and the identity of the fund holder remains anonymous. The Ledger CTO previously questioned whether the movements truly resemble a white-hat operation, noting that the tactics diverge from typical responsible disclosure patterns. The community remains split on whether the actors are genuine security researchers or opportunists leveraging a public stance to extract a finder's fee.
Sources
- CryptoSlate, "A whitehat hacker is holding $320 million in drained Bitcoin until developers prove they patched a fatal network flaw," September 7, 2026. https://cryptoslate.com/a-whitehat-hacker-is-holding-320-million-in-drained-bitcoin-until-developers-prove-they-patched-a-fatal-network-flaw/
- Bitcoin Magazine, "Alleged White-Hat Hackers Withdraw 4,000 Bitcoin From Blockstream's Liquid Network Federation Reserves," September 6, 2026. https://bitcoinmagazine.com/news/alleged-white-hat-hackers-withdraw-4000-bitcoin-from-blockstreams-liquid-network-federation-reserves
- DailyCoin, "Liquid Network Hack Takes a Twist: Hackers Offer to Return $320 Million," September 7, 2026. https://dailycoin.com/liquid-network-hack-320-million-bitcoin/
