Besides the username, what other sensitive information is displayed in clear text from the ftp header?

The password. 
FTP is an acronym for "File Transfer Protocol", it is a standard network protocol or communication protocol used to transfer files (for uploading or downloading files) between a server and a client, that is, the providers of a service (server) and the requesters of said service (client), on a computer network. Normally FTP servers require a password and username but it is cleartext, "a clear-text sign-in protocol". So concluding, other sensitive information that is displayed in clear text from the ftp header is the password.

Program;