CVE 2007-2165
The Auth API in ProFTPD before 20070417, when multiple simultaneous authentication modules are configured, does not require that the module that checks authentication is the same as the module that retrieves authentication data, which might allow remote attackers to bypass authentication, as demonstrated by use of SQLAuthTypes Plaintext in mod_sql, with data retrieved from /etc/passwd.
See the 
CVE page on Mitre.org
for more details.
