After the weekend compromise of phpbb.com's site, it has been confirmed that:

The attackers were able to obtain access to the phpBB.com and area51 databases, meaning that user information, including hashed salted passwords, was compromised.
This means if you were a member there and used the same password elsewhere, it would be extremely wise to change it.

In case anyone lands here and thinks perhaps there may be a security vulnerablity in the phpBB software, rest assured that:

We have confirmed that initial entry was made via a team member's compromised login details and not as the result of a vulnerability in the phpBB software.
phpBB.com currently remains down while they rebuild their systems and verify integrity. This is the reason why there is no current version info in the ACP.

To view the sources of these quotes, visit any phpBB.com page. You may also find further updates there.