It has been revealed that Valve's Steam service has been hacked and many accounts have been compromised, yet Valve remains mostly silent on the leak. All Steam users (so, everyone reading this here) should be wary of any password reset e-mails they receive. Receiving such an e-mail does not mean your account has been compromised, but can mean that your account is being targeted.
The attack is taking advantage of a flaw in the Steam forgotten password service, allowing the attacker to completely bypass the normal security code entry. It is currently unclear if Steam Guard provides sufficient protection from the exploit. It appears Valve have already closed this loophole, but not before many users were already affected.
For complete information (at least until Valve releases their own statement), please read http://masterherald.com/steam-hit-by-major-security-breach-many-accounts-hacked/