The breed function in the smart contract implementation for Farm in Seal Finance (Seal), an Ethereum token, lacks access control and thus allows price manipulation, as exploited in the wild in December 2020 and January 2021.
https://etherscan.io/address/0x33c2da7fd5b125e629b3950f3c38d7f721d7b30d
https://blocksecteam.medium.com/security-incident-on-seal-finance-fa79c27a1c3b