FileZilla v3.53.1, Windows 10 x64. The screenshot says it all. Why is this happening? I've never seen this before with any FTP server in the Net. Weird. Spoiler: for the search feature This server does not support TLS session resumption on the data connection. TLS session resumption on the data connection is an important security feature to protect against data connection stealing attacks. If you continue, transferred files may be intercepted or their contents replaced by an attacker.