Beosin: Gnosis Omni Bridge cross-chain bridge project has a replay vulnerability at the contract level

The Beosin security team found that after Ethereum merged and forked out of ETHW, the Gnosis Omni Bridge cross-chain bridge project did not actually verify the chainID of the current chain because of the hard-coded chainID in the contract code, which caused the contract to verify the signature. Verification passed on the forked chain. The attacker first transferred WETH through the Omni Bridge on the ETH main network, and then replayed the same transaction content on the ETHW chain to obtain an equal amount of ETHW. At present, the attacker has transferred 741 ETHW to the exchange. The Beosin security team recommends that if the chainID is preset in the contract of the project party, please manually update the chainId first. Even if the project party decides not to support ETHW, since it is impossible to completely isolate the flow of assets through the cross-chain bridge, it is recommended that all be on the ETHW chain renew.