Pike Finance integrated with Circles cross chain USDC protocol CCTP. This works by off-chain signers sending an attestation that an event occurred once finality has been reached out chain A to the contract on chain B. There were two vulnerabilities in this case. The first issue was a lack of input validation on CCTP for the intended receiver and the amount. Working on many cross-chain protocols, there is information that is set by the users that is application specific, meaning it must be specified by the integrator. I couldn't find any more details on what went wrong besides the information above. Nobody pointed to the contract and said what was actually wrong with it and I didn't see the source code. This appears to be the exploit transaction on Optimism. I see USDC being moved around but can't find source for the Beta protocol so it's hard to tell. Unluckily enough, there is a second issue. While trying to deploy a patch for the first issue, the storage layout got messed up. As a result, what was the initialized value was overwritten with a zero. Hence, an attacker was able to call this themselves to become the admin of the protocol. With this, they could call admin functions to drain all of the funds. Cross-chain bridging protocols are hard to interact with securely! The second bug was a real bad mishap yet an interesting note to have fork tests for deployment upgrades.