A critical censorship vulnerability in Optimism's sequencer rate limiter allowed attackers to censor specific accounts by replaying cross-chain signed transactions without validating chain IDs, affecting approximately 1.3 million accounts including major protocols like LayerZero and Uniswap. The bug exploited the fact that rate limits were incremented before EIP-155 validation, enabling indefinite transaction censorship via trivial transaction spam.
GitHub published a detailed postmortem of three major availability incidents (Feb 2, Feb 9, Mar 5) caused by rapid usage growth, architectural coupling in authentication/user management database clusters, insufficient load shedding mechanisms, and latent failover configuration issues. The incidents revealed single points of failure across critical infrastructure including Actions runners and Redis clusters, with mitigation strategies including user cache redesign, infrastructure isolation, and migration to Azure.