Summary

You should always check for sequencer availability when using price feeds from layer 2 chains.

Vulnerability Details

Optimistic rollup protocols move all execution of the layer 1 (L1) Ethereum chain, complete execution on a layer 2 (L2) chain, and return the results of the L2 execution back to the L1. These protocols have a sequencer that executes and rolls up the L2 transactions by batching multiple transactions into a single transaction.

If a sequencer becomes unavailable, it is impossible to access read/write APIs that consumers are using and applications on the L2 network will be down for most users without interacting directly through the L1 optimistic rollup contracts. The L2 has not stopped, but it would be unfair to continue providing service on your applications when only a few users can use them.

Impact

If the L2 Sequencer goes down, oracle data will not be kept up to date, and thus could become stale.

Tools Used

Visual Studio Code

Recommendations

Check this example -> https://docs.chain.link/data-feeds/l2-sequencer-feeds#example-code