## Description Malicious actors can watch any `selectWinner` transaction and front-run it with a transaction that calls `refund` to avoid participating in the raffle if he/she is not the winner or even to steal the owner fess utilizing the current calculation of the `totalAmountCollected` variable in the `selectWinner` function. ## Vulnerability Details The PuppyRaffle smart contract is vulnerable to potential front-running attacks in both the `selectWinner` and `refund` functions. Malicious actors can monitor transactions involving the `selectWinner` function and front-run them by submitting a transaction calling the `refund` function just before or after the `selectWinner` transaction. This malicious behavior can be leveraged to exploit the raffle in various ways. Specifically, attackers can: 1. **Attempt to Avoid Participation:** If the attacker is not the intended winner, they can call the `refund` function before the legitimate winner is selected. This refunds the attacker's entrance fee, allowing them to avoid participating in the raffle and effectively nullifying their loss. 2. **Steal Owner Fees:** Exploiting the current calculation of the `totalAmountCollected` variable in the `selectWinner` function, attackers can execute a front-running transaction, manipulating the prize pool to favor themselves. This can result in the attacker claiming more funds than intended, potentially stealing the owner's fees (`totalFees`). ## Impact - **Medium:** The potential front-running attack might lead to undesirable outcomes, including avoiding participation in the raffle and stealing the owner's fees (`totalFees`). These actions can result in significant financial losses and unfair manipulation of the contract. ## Recommendations To mitigate the potential front-running attacks and enhance the security of the PuppyRaffle contract, consider the following recommendations: - Implement Transaction ordering dependence (TOD) to prevent front-running attacks. This can be achieved by applying time locks in which participants can only call the `refund` function after a certain period of time has passed since the `selectWinner` function was called. This would prevent attackers from front-running the `selectWinner` function and calling the `refund` function before the legitimate winner is selected.