Deniz 
A major accomplishment for the Ethereum-based ecosystem was Optimism’s launch of permissionless fraud proofs, a technology also called as fault proofs that lets users contest perhaps fraudulent or erroneous transactions on layer-2 networks. Unlike permissionless fraud proofs, which offer that technique to all users, permissioned fraud proofs only let trusted proposers contest transactions.
Stage 1 Decentralization and Vitalik Buterin’s Vision
As Ethereum co-founder Vitalik Buterin describes, Optimism could assert that we could reach Stage 1 decentralization with progress. Stage 1, sometimes known as “limited training wheels,” calls for a functioning fraud-proof system in a layer-2 network, even if a multisignature of trusted individuals could reserve the power to override the system should any flaws be found or exploited.
But just over two months after the permissionless fraud proofs went live on June 10, the Optimism Foundation has reversed the network back to a permissioned state following “community-driven audits” revealing a variety of flaws at differing degrees of severity, Optimism said on X.
A representative of Optimism contributor OP Labs presented a proposal to the governance forum of Optimism, summarizing the security flaws found and the grounds for turning on the fallback system.
“None of the vulnerabilities have been exploited, and user assets are not and were never at risk. However, out of an abundance of caution, the permissioned fallback mechanism has been activated in order to avoid any potential instability while the vulnerabilities are patched,” protocol engineer Mofi Taiwo said.
Discovery of Severe Vulnerabilities and Upcoming Granite Upgrade
Based on the ImmuneFi bounty scale of Optimism , two highly severe vulnerabilities were found among the discovered ones. “While the auditors did discover some high-severity issues, no user assets were ever at risk. All of the audit issues listed below can be detected by our monitoring tooling,” Taiwo’s post states.
Although the fallback systems had been under audit, some contracts pertaining to the fraud proof system were outside Optimism purview. “The dispute game and MIPS contracts fall into the liveness/reputational risk category, which does not require audits. The fallback mechanisms make any bugs simple to recover from and pose no risk to user funds. Therefore, we have opted not to pursue a fix review for the changes made in this proposal.”
Taiwo’s suggestion would set the September 10 upgrade for 16:00:01 UTC. Dubbed “Granite,” the upgrade calls for multiple network changes, including an L2 hard fork. Taiwo’s post states that although the hard fork has not been audited, OP Labs checked the modifications and found them low-risk.
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