A multi-merchant purchasing system is configured to identify downloadable products selected by a user for purchase. The identified downloadable products are offered by multiple merchants. The multi-merchant purchasing system enables the user to purchase all of the downloadable products in a single transaction. Specifically, the multi-merchant purchasing system determines payment information associated with the user and, with minimum user-interaction, sends the payment information to applications associated with the merchants for processing. The multi-merchant purchasing system may also be configured to receive purchase information from the merchant applications and maintains the purchase information for the user in a locker. The multi-merchant purchasing system may further be configured to automatically download and install the purchased product onto the user's computing device through a software assistant. To ensure privacy and security, the multi-merchant purchasing system may include a credit card quarantine module to secure credit card data by encoding and multiple levels of encryptions. The multi-merchant purchasing system may be further configured to accept a request to collect extended user data related to the user on behalf of merchants and return the collected extended user data to the merchants.