OP Labs, the team behind the Ethereum layer 2 network Optimism, has fixed two problems with the fraud proof system used on the testnet. Offchain Labs, creators of Arbitrum, a competing layer 2 network, alerted OP Labs about these vulnerabilities.

Ed Felton, cofounder of Offchain Labs, revealed in a recent blog post that they informed OP Labs about the issues on March 22 but waited until the flaws were fixed on April 25 before informing the wider community.

The vulnerabilities could have allowed someone to trick the OP Stack fraud proof mechanism into accepting a fake chain history or prevent it from accepting the correct one. These problems were due to flaws in how the timer-handling code was designed.

Felton mentioned that OP Labs has made changes to their timer-handling code to address these issues. It's important to note that these issues were discovered on the testnet, where developers experiment and fix problems before implementing updates on the mainnet.

In their own blog post, OP Labs thanked the Offchain Labs team for reporting the issues with their FaultDisputeGame contract. They acknowledged that while safety measures would have caught this bug, it could have caused disruptions for users if it had occurred on the main network.

Previously, OP Labs initiated a Sherlock audit contest for their proposed fault proof system, reporting no critical vulnerabilities that could bypass existing safety measures. This incident highlights the importance of collaboration in maintaining the security and stability of blockchain networks.

In conclusion, the prompt actions taken by both teams demonstrate the commitment to improving the security of layer 2 solutions, ensuring a safer environment for users of Ethereum and other blockchain networks.