security - In general, is SFTP unsecure?

I've seen several comments on internet in which people say something like:

"I've uninstalled SFTP server, it is much better, it remove security vulnerabilities"

What are these vulnerabilities, if there are any?

Answer

SFTP runs over SSH, although some servers use a separate executable for them. Whatever vulnerabilities that executable may have is what you're being protected from (although I've not heard of any myself). The protocol itself is as secure as your SSH server.