On an L2 (Arbitrum/Optimism/Base), the contract reads a Chainlink price without first checking the sequencer-uptime feed. During a sequencer outage the price feed goes stale while the L2 later replays transactions, letting users act on an outdated price.
// sequencer goes down; price freezes at 2000. // on recovery, queued tx borrows at 2000 while true price is 1500 // -> instant bad debt.
(, int256 up,, uint256 since,) = sequencerUptimeFeed.latestRoundData(); require(up == 0 && block.timestamp - since > GRACE_PERIOD, "sequencer down");
Largest recorded losses in the same failure class — related, not the same bug:
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