From a Ubisoft email.

Dear Member,

We recently found that one of our Web sites was exploited to gain unauthorized access to some of our online systems. We instantly took steps to close off this access, to begin a thorough investigation with relevant authorities, internal and external security experts, and to start restoring the integrity of any compromised systems.

During this process, we learned that data were illegally accessed from our account database, including user names, email addresses and encrypted passwords. No personal payment information is stored with Ubisoft, meaning your debit/credit card information was safe from this intrusion.

As a result, we are recommending you to change your password by clicking this link.

Out of an abundance of caution, we also recommend that you change your password on any other Web site or service where you use the same or a similar password.

An official forum thread has been created for you to post your questions.

We sincerely apologize for any inconvenience and thank you for your understanding.
We sincerely apologize to all of you for the inconvenience. Please rest assured that your security remains our priority.

The Ubisoft team