immeas - sequencer uptime is not validated in ChainlinkOracle

[sherlock-admin]

immeas

medium

sequencer uptime is not validated in ChainlinkOracle

Summary

Lack of validation if the Arbitrum sequencer is up in Chainlink oracle

Vulnerability Detail

It is best practice to verify that not only the price is up to date but also that the sequencer is up on L2 chains:
https://docs.chain.link/data-feeds/l2-sequencer-feeds

See this:
sherlock-audit/2023-04-blueberry-judging#142

Impact

Over-borrowing JUSD or unwanted liquidations can happen due to outdated prices.

Code Snippet

https://github.com/sherlock-audit/2023-04-jojo/blob/main/smart-contract-EVM/contracts/adaptor/chainlinkAdaptor.sol#L43-L55

https://github.com/sherlock-audit/2023-04-jojo/blob/main/JUSDV1/src/oracle/JOJOOracleAdaptor.sol#L26-L35

Tool used

Manual Review

Recommendation

https://docs.chain.link/data-feeds/l2-sequencer-feeds

Duplicate of #101