http://ubuntuforums.org/announce.html

Ubuntu Forums is down for maintenance

There has been a security breach on the Ubuntu Forums. The Canonical IS team is working hard as we speak to restore normal operations. This page will be updated regularly with progress reports.
What we know

>>>>>Unfortunately the attackers have gotten every user's local username, password, and email address from the Ubuntu Forums database.
The passwords are not stored in plain text. However, if you were using the same password as your Ubuntu Forums one on another service (such as email), you are strongly encouraged to change the password on the other service ASAP.
Ubuntu One, Launchpad and other Ubuntu/Canonical services are NOT affected by the breach.

Progress report

2013-07-20 2011UTC: Reports of defacement
2013-07-20 2015UTC: Site taken down, this splash page put in place while investigation continues.

If you're using Ubuntu and need technical support please see the following page for support:

Finding Help.

If you're looking for a place to discuss Ubuntu, in the meantime we encourage you to check out these sites:

The Ubuntu subreddit
The Ubuntu Community on Google+
Ubuntu Discourse