Katpolice

Somewhat Threatening Sniper
So apparently, steam right now is down due to some cache/date issue and a security issue.

Basically the problem is whenever you look at your account details your'll end up looking at someone else. Meaning their personal information and whatnot is exposed. Now, this bad. Really bad. Expressly, during the winter sale.

What does this mean?

It means that their's a chance that someone viewed/viewing your account details (eg. Original profile name, email, phone number, etc)

How about credit card information?

It means that it could be exposed and/or looked at. I suggest you watch your payment methods for unauthorized purchases and account activity. However, if programmed this correctly their shouldn't be any unauthorized purchases.

Where can I get more information about this security issue?

Theirs a thread right now, on Reddit which trending around this topic. You view it here:
https://www.reddit.com/r/Games/comments/3y7maa/something_is_really_wrong_with_steam_be_careful/

Short link: https://redd.it/3y7maa

DO NOT POST PERSONAL INFORMATION OF OTHER USERS! You should only send this to Valve as evidence of a breach. It is protected information for a reason!