If you’re like me and you wanted to go and buy someone a copy of Bad Rats their morning, only to find that the Steam storefront was down, well, here’s the reason why.
Last week, a vulnerability allowed others access to your account provided they had your username. This was done from a loophole in the password request system. It’s since been fixed (hence the downtime earlier), but the exploit may have been available since the 21st.
There is some good news. Valve seems to be able to detect who may have been effected, and will be issuing password resets to those impacted. Also, if you had Steam Guard enabled, then you should be fine, as it’s a two-step process based on hardware. Still, that would only impact someone’s ability to log in, and passwords for those with Steam Guard may have been modified.