Symbiosis Bridge mints 2^62 fake syBTC; 15 BTC recovered

On Sept. 11 at about 04:28 UTC, a transaction accepted as signed by Symbiosis’s BridgeV2 minted roughly 2^62 units of syBTC, the protocol’s synthetic bitcoin token, to a newly created wallet on BNB Chain. A security firm reported the wallet later sold about 4.39 WBTC on Ethereum, generating roughly $336,000 in proceeds. Symbiosis reported it has recovered about 15 BTC to date; those funds are secured in a team-controlled multisignature wallet. Final accounting is ongoing and liquidity providers have not yet been reimbursed.

Only the native Bitcoin Bridge was affected. Other routes and components, including connections across EVM chains, TRON and TON, remained operational and the protocol’s relayer group continued functioning. Bitcoin swaps routed through partners Chainflip and THORChain were restored, while the native Symbiosis Bitcoin Bridge remains paused to keep traffic off the compromised route.

Symbiosis is contacting each affected liquidity provider directly and is building a compensation framework but has not published eligibility criteria, the method for calculating payments or a timetable for reimbursements. The protocol offered a 20% white-hat bounty through Sept. 13; after that window the protocol stated the same percentage will be offered to anyone who provides information that leads to recovery. The announcement did not specify an exact cutoff time or timezone for the bounty window.

The observed WBTC sales and the recovered 15 BTC are not a final loss tally. Symbiosis reported it will publish confirmed loss and exposure figures and a full accounting in a subsequent update. Affected liquidity providers are awaiting those figures, the compensation criteria and any decision about restarting the native bridge.