SQL injection vulnerability in ProFTPD Server 1.3.1 through 1.3.2rc2 allows remote attackers to execute arbitrary SQL commands via a "%" (percent) character in the username, which introduces a "'" (single quote) character during variable substitution by mod_sql.

More... (http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2009-0542)