Embodiments of the systems and methods described herein can detect that a user is accessing a payment webpage of a website associated with a merchant. The system can cause a window requesting authentication credentials associated with an account of the user to appear on a display of a computing device associated with the user. After the system has received and verified the authentication credentials, the system can create a merchant-specific virtual card linked to a pre-existing payment instrument associated with the account. The system can enter information associated with the merchant-specific virtual card in a payment section of the payment webpage. After receiving an authorization request for a transaction using the merchant-specific virtual card, the system can authorize the transaction based on a balance of the pre-existing payment instrument.