SponsorshipPaymaster is a token-based Paymaster that allows user to pay gas fees in ERC-20 tokens. Paymasters can sponsor transaction fees for contract accounts. The ERC-4337 Entrypoint verifies whether the Paymaster has a sufficient deposit or if the contract account holds enough funds to cover gas fees. During execution, if a Paymaster is involved, it can implement custom fee logic.

Zellic conducted a security assessment for Biconomy Labs from November 9th to November 10th, 2023. During this engagement, Zellic reviewed SponsorshipPaymaster's code for security vulnerabilities, design issues, and general weaknesses in security posture.