Visa testing credit card gas fee payments through Paymaster Smart Contracts

Visa ran an experiment in which users pay blockchain gas fees with Visa cards, using a paymaster web service built on Cybersource and a Verifying Paymaster Smart Contract under the ERC-4337 standard. The wallet sends the User Operation and card credentials to the web service, which charges the user in fiat currency and then produces a digital signature over the calldata and gas fee information, valid for a set time window. The wallet appends this signature and window to the User Operation, and the paymaster contract checks it, covering gas costs only if the signature is correct. The time window guards against users paying in fiat when ETH is cheap and later redeeming the signature when it is more expensive. The article says merchants or dApps could run their own paymaster solutions using this approach, but notes the product is still in development and its final version may differ.