Excess ETH Sent by User is Not Handling in `tillIn` Function
Github
https://github.com/Cyfrin/2024-08-tadle/blob/04fd8634701697184a3f3a5558b41c109866e5f8/src/core/TokenManager.sol#L56
Summary
The tillIn function in the TokenManager contract fails to refund excess Ether when a user sends more Ether than the specified _amount. This can lead to unintended financial loss for users, which is a significant usability issue and may damage trust in the contract's operations.
Vulnerability Details
The tillIn function checks if the msg.value is less than the _amount required. If true, it reverts the transaction. However, there is no logic to handle cases where msg.value exceeds _amount. The excess Ether is not refunded, leading to a potential loss for the user. If a user accidentally sends more Ether than required, the excess Ether is not refunded, resulting in a loss for the user.
For example, if _amount is 1 ETH and msg.value is 2 ETH, the contract will keep the extra 1 ETH without refunding it. Users might unintentionally lose funds if they overpay due to mistakes or misunderstandings, which could damage trust in the contract.
Impact
This issue is significant because it can lead to unintentional financial loss for users. While it may not be a critical security vulnerability, it is a serious usability issue that could cause frustration and loss of trust in the contract's operations.
Tools Used
Manual Review
Recommendations
Refund excess Ether to the users, this ensures that users do not lose funds due to accidental overpayment.
Lead Judging Commences
[invalid] finding-TokenManager-tillin-excess
Invalid, these are by default, invalid based on codehawks [general guidelines](https://docs.codehawks.com/hawks-auditors/how-to-determine-a-finding-validity#findings-that-may-be-invalid). The check implemented is simply a sufficiency check, it is users responsibility to only send an appropriate amount of native tokens where amount == msg.value when native token is intended to be used as collateral (which will subsequently be deposited as wrapped token). All excess ETH can be rescued using the `Rescuable.sol` contract. > Users sending ETH/native tokens > If contracts allow users to send tokens acc111identally.
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