ChainCatcher news, according to the Slow Mist security team's intelligence, the Numbers Protocol (NUM) token project on the ETH chain has been attacked, with the attacker profiting approximately $13,836.The Slow Mist security team shared the following in a brief:The attacker created a malicious anyToken token, which is the attack contract (0xa68cce), and the underlying token of this malicious token contract points to the NUM token address;Then, they called the anySwapOutUnderlyingWithPermit function of the Router contract of the Multichain cross-chain bridge. This function takes anyToken as input and calls the permit function of the underlying token for signature approval, then exchanges the authorized user's underlying token to a specified address. However, since the NUM token does not have a permit function and has a callback feature, even if the attacker inputs a fake signature, it can still return normally, causing the transaction not to fail, resulting in the NUM tokens of the victim's address being ultimately transferred to the specified attack contract;The attacker then exchanged the profited NUM tokens for USDC through Uniswap and then converted them to ETH for profit;The main reason for this attack is that the NUM token does not have a permit function and has a callback feature, allowing fake signatures to deceive the cross-chain bridge, leading to unexpected transfers of user assets. (Source link)