I wouldn't jump to any conclusions, though it does seem suspicious. My wife's card was just used fraudulently over the last two weeks, which is about the third or fourth time it's happened since she's had that card. Some how, I've managed to dodge that issue, thankfully, we have a card company (chase) that is excellent in these types of situations. It could be tied to the recent equifax breach as well, you just never know.
About the only thing you can do when purchasing something online, is ensure that the address is https, rather than just http, the "s" is for secure, and the hope is that it truly denotes a secure connection.