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Cross-chain protocol Symbiosis says it recovered about 15 BTC after an attacker exploited its Bitcoin Bridge and minted billions of unbacked syBTC. The recovered Bitcoin is now held in a team-controlled multisig wallet.
The Sept. 11 attack forced Symbiosis to pause its native Bitcoin Bridge while leaving its other cross-chain routes operational. Bitcoin swaps have since returned through Chainflip and THORChain, but the affected bridge remains offline.
Attacker Minted 46.1B Unbacked SyBTC On BNB Chain
Blockchain security firm Blockaid detected a transaction involving Symbiosis’s BridgeV2 contract on BNB Chain that minted about 46.1 billion syBTC to a newly created address. The tokens were not backed by an equivalent amount of Bitcoin.
Most of the newly minted supply was not converted into other assets during the activity traced by Blockaid. The security firm identified about 4.39 WBTC sold through Uniswap v4 on Ethereum, generating roughly $336,000 in proceeds at the time of its alert.
The 46.1 billion syBTC mint therefore does not represent the protocol’s confirmed financial loss. Symbiosis has not published its final accounting and said it would release confirmed figures after completing its review.
Native Bitcoin Bridge Remains Offline After September 11 Exploit
Symbiosis said the vulnerability was limited to its Bitcoin Bridge, which it isolated from the rest of the protocol. Routes covering EVM networks, Tron and TON continued operating, while Octopools and the protocol’s relayer network were also unaffected.
Bitcoin swaps were later restored through external integrations with Chainflip and THORChain. Symbiosis has not reopened its native Bitcoin Bridge and said a separate update would precede its return.
Symbiosis Prepares Compensation Plan After Recovering 15 BTC
The protocol offered the attacker a white-hat bounty equal to 20% of returned funds through Sept. 13. Symbiosis said the same percentage would then be offered to anyone providing information that leads to further recovery.
Symbiosis is also contacting affected liquidity providers directly and preparing a compensation framework. Final losses, compensation terms and the timetable for reopening the native Bitcoin Bridge remain undisclosed.
