CRLF injection vulnerability in Microsoft Internet Explorer 5 and 6 allows remote attackers to execute arbitrary FTP commands via an ftp:// URL that contains a URL-encoded CRLF (%0D%0A) before the FTP command, which causes the commands to be inserted into an authenticated FTP connection established earlier in the same browser session, as demonstrated using a DELE command, a variant or possibly a regression of CVE-2004-1166.  NOTE: a trailing "//" can force Internet Explorer to try to reuse an existing authenticated connection.