No check if Arbitrum/Optimism L2 sequencer is down in Chainlink feeds `ChainlinkOracle.sol`
Summary
Chainlink recommends that all Optimistic L2 oracles consult the Sequencer Uptime Feed to ensure that the sequencer is live before trusting the data returned by the oracle.
If the Arbitrum Sequencer goes down, oracle data will not be kept up to date, and thus could become stale. However, users are able to continue to interact with the protocol directly through the L1 optimistic rollup contract. You can review Chainlink docs on https://docs.chain.link/data-feeds/l2-sequencer-feedsfor more details on this.
Impact
If the Arbitrum sequencer goes down, the protocol will allow users to continue to operate at the previous (stale) prices. This will break all the core functionality in the protocol.
Recommendations
Recocmmand follow the steps in https://docs.chain.link/data-feeds/l2-sequencer-feeds#example-code
Lead Judging Commences
invalid_sequencer_status_chainlink_and_L2
LightChaser: ## [Medium-6] Missing checks for whether the L2 Sequencer is active ## [Low-22] Chainlink sequencer status is not checked
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