We recently had fraudulent charges on our Costco CC. It started out with 2 small Amazon purchases. We have an Amazon CC, used exclusively for Amazon, so obviously fraudulent charges. I did dispute the charges yet as we were going on a trip and I needed to use the card. About a week later, there was a purchase of almost $1,000 for what I assume was a phone by the description. Citibank flagged it and I called which cancelled the card. About a month later, my wife's Costco CC had 2 fraudulent charges of about $190 for a membership and $89 from Amazon again, which I immediately disputed. Her card was cancelled.
I originally thought my card was skimmed somewhere, but with my wife's CC getting hit too, I now assume some sort of data breach. More concerning, is that when I disputed the Amazon charge, a question came up saying it was a Wallet charge. My wife doesn't even know how to pay with her iPhone Wallet, so doesn't have her Costco CC on it and our Amazon account has our Amazon CC in it's wallet.