OpenZeppelin Contracts for Cairo is a library for secure smart contract development written in Cairo for StarkNet, a decentralized ZK Rollup. "is_valid_eth_signature" is missing a call to "finalize_keccak" after calling "verify_eth_signature". As a result, any contract using "is_valid_eth_signature" from the account library (such as the "EthAccount" preset) is vulnerable to a malicious sequencer. Specifically, the malicious sequencer would be able to bypass signature validation to impersonate an instance of these accounts. The issue has been patched in 0.6.1.