For those who haven't seen Coinbase's answer:
Update as of 9:37 AM PST on February 15, 2018
We are actively investigating some reports from our customers about unexpected credit or debit card charges appearing on their statements from previous Coinbase purchases.
We can confirm that the unexpected charges are originating from our payment processing network, and are related to charges from previous purchases. To the best of our knowledge, these unexpected charges are not permanent and are in the process of being refunded. We are running joint investigations with all parties involved, and will provide updates as we receive them.
We apologize for the trouble, and are working as quickly as possible to help anyone affected by this.
Minor update in wording at 10:31 AM PST for better clarity.
HOW YOU CAN HELP
Please let us know by commenting here if you have been affected by these charges, and provide the following info:
[debit, credit, or bank transfer], [your country], [which bank you saw the additional charge on], [number of additional charges], [delay since original transaction], [is the charge posted or pending], [your case number]
Example: debit, US, MYBANK, 1, 1 day, pending, #100001
Your reports will go a long way toward helping us track down what may be happening here and reaching a quick resolution. We will follow up via your case in order to collect additional info if needed, so please make sure to include a case number!
Once again, we apologize for the poor experience.
[1]
https://www.reddit.com/r/CoinBase/comments/7xs1aq/update_on_multiple_charges/