The transferFrom function of a smart contract implementation for Useless Ethereum Token (UET), an Ethereum ERC20 token, allows attackers to steal assets (e.g., transfer all victims' balances into their account) because certain computations involving _value are incorrect, as exploited in the wild starting in December 2017, aka the "transferFlaw" issue.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.