On July 28, 2021, PolyYeld Finance was exploited when attackers discovered that the Masterchef contract could not properly handle xYELD's transfer tax reward distribution system. Attackers minted approximately 4.995 billion YELD tokens and converted 4% of them to ~123 ETH (~$250K) before the token crashed 100%.

The profit farming agreement PolyYeld Finance was attacked. The project contract was used to mint 4.9 trillion YELD tokens and dump them in the secondary market.