This is why I never save my credit card info in any of my online accounts, even things like paypal. I only ever order something online like once or twice a month, and while it certainly does take a bit longer to pay when you have to manually enter the credit card info every time, the added security is worth it. Even if someone hacks my account, with no credit card info associated with it they can't do anything financially damaging with it, really. So, anyone who does keep their credit card info saved in their Steam account, ask yourself this: how often do you actually buy games over Steam, and is the added inconvenience of a 2 minutes longer ordering process every time worth the risks?
Also, changed my steam password without any issues.