From the Debian advisory:
The vulnerable-passwords scripts introduced for CVE-2011-0009
failed to correct the password hashes of disabled users.
Several cross-site scripting issues have been discovered.
Password hashes could be disclosed by privileged users.
Several cross-site request forgery vulnerabilities have been
found. If this update breaks your setup, you can restore the old
behaviour by setting $RestrictReferrer to 0.
The code to support variable envelope return paths allowed the
execution of arbitrary code.
Disabled groups were not fully accounted as disabled.
SQL injection vulnerability, only exploitable by privileged users.