Back in June, Bethesda Softworks was hacked by the infamous group called LulzSec. While back then Bethesda's Matt Grandstaff stated "These attacks will be evaluated to determine if there are any additional protections we might take that would be prudent", unfortuantely these additional protections were not enough to prevent another attack.
Bethesda forum users have received the following e-mail (if you are a registered user and you haven't, check your spam box):
We have identified a potential breach of our forum user database that occurred Friday morning, Aug 12. We have reset your forum password as a precaution, in the event that any encrypted forum user passwords were compromised.
When you next try to login to the forums, your old password will not work. Click the "I've forgotten my password link" underneath the login boxes, and follow the steps to setup a new password for your account.We recommend you do not use your old password or a password you have used for other sites. Further, if your old forum password was used for any other online purposes, we recommend changing the password on those accounts as well.
Remember to change your passwords immediately, including your Wikia passwords if you happened to use the same password here as in Bethesda forum.