UPDATED | February 17, 2018:
In a surprise twist, Visa has reversed its position and declared, "This issue was not caused by Coinbase," in an official statement.
Without taking direct responsibility for the error which caused the overcharging, Visa went on to say it was working with Coinbase and payment processing company Worldpay to reimburse all customers who were effected.
Details on what actually transpired are still sparse. It may amount to small consolation that Visa professed, "We deeply regret any inconvenience this may have caused customers."
UPDATED | February 16, 2018:
Yesterday, Coinbase suggested that blame for the overcharging debacle may lie with Visa:
But today, a spokesperson for the credit card company refuted this, saying, "Visa has not made any systems changes that would result in the duplicate transactions cardholders are reporting. We are also not aware of any other merchants who are experiencing this issue."
The statement from Visa went on to include, "We are reaching out to this merchant's acquiring financial institution to offer assistance and to ensure cardholders are protected from unauthorized transactions."
ORIGINAL | February 15, 2018:
Coinbase has issued a statement today to acknowledge errors related to purchases of cryptocurrencies on the exchange made with credit cards have resulted in "additional charges and/or refunds."
According to Coinbase, purchases that took place on the exchange between January 22 and February 11, 2018 were affected by the changing of a merchant category code (MCC) initiated by major credit card networks at the behest of banks and card issuers. The call to change the MCC may be related to an inability of the credit card companies to process returns.
At least one user complained on reddit that after a week of "canned response" from Coinbase support, they were left with a negative bank balance, unable to pay rent. Other reddit users also claim to have been charged multiple times by the exchange – in some cases as many as 15 and 17 times.
Coinbase pledges that "each affected customer will be refunded in full for any erroneous charge." It is expected that such refunds will appear in user accounts in the days to follow, and the exchange has asked anyone who believes they have been inappropriately charged to reach out to card issuers or banks, and to its support team at email@example.com.
This isn't the first time Coinbase has run into trouble with charges; it also refunded customers who saw double-spends on their bank accounts in May of 2016.