Front-Running Vulnerability in Daily Claim Limit

Description

The dailyClaimLimit imposes a strict cap of 100 claims per day, enforced through a first-come, first-served mechanism tied to dailyClaimCount and reset via lastFaucetDripDay. This design exposes the protocol to front-running by MEV bots, which monitor the mempool and insert their transactions ahead of legitimate users' submissions, effectively monopolizing available slots at reset times and transforming equitable token distribution into a high-stakes race dominated by speed and resources.

Risk

Likelihood:

• Demand surges near daily resets, especially with the 3-day individual cooldown amplifying competition for the limited 100 slots.

• Mempool visibility enables sophisticated actors to detect and preempt user transactions in real-time.

Impact:

• Legitimate participants, particularly those without advanced tooling, are systematically excluded, fostering inequality and eroding trust in the faucet's fairness.

• The low cap (100 users/day) exacerbates scarcity, potentially leading to user abandonment and suboptimal protocol adoption, while benefiting a small cadre of privileged frontrunners.

Proof of Concept

POC Explanation: By setting the limit to 1, the test simulates a user submitting a claim, only for a bot to front-run it successfully. The user's transaction then fails due to the cap, demonstrating how bots can systematically capture slots, leaving genuine users empty-handed.

Recommended Mitigation

Addressing front-running in this context requires a fundamental redesign of the claim eligibility and distribution logic, as the current first-come model inherently favors speed over equity. One viable approach involves shifting to a proof-of-work (PoW)-inspired eligibility system, where users must demonstrate sustained engagement rather than raw transaction speed. For instance, eligibility could be granted only after a user successfully interacts (e.g., queries or pings the contract) once per day for 10 consecutive days following a 24-hour reset window—verifying commitment without computational waste. Upon meeting this threshold, the user receives their drip, and the eligibility counter resets for the next cycle.

To scale this, the daily cap should be substantially increased to around 10,000 eligible users per day, allowing far broader access while maintaining scarcity through the PoW-like filter. Users who fail to meet the criteria simply defer to the next day, promoting inclusivity over frenzy. This overhaul would transform the protocol from a volatile rush into a merit-based, patient-driven system, but it demands significant changes: new state variables for tracking daily interactions, multi-phase verification functions, and potentially off-chain signaling for user guidance. Such modifications could alter core assumptions about the faucet's simplicity and gas efficiency, necessitating thorough testing and community input to ensure alignment with the protocol's testnet utility goals.