The File Transfer Protocol (FTP) has long been a convenient file exchange mechanism between computers on a network. While this standard protocol has been supported in all major browsers almost since its inception, it’s by now one of the oldest protocols still in use and suffers from a number of serious security issues.
The biggest security risk is that FTP transfers data in cleartext, allowing attackers to steal, spoof and even modify the data transmitted. To date, many malware distribution campaigns launch their attacks by compromising FTP servers and downloading malware on an end user’s device using the FTP protocol.
Aligning with our intent to deprecate non-secure HTTP and increase the percentage of secure connections, we, as well as other major web browsers, decided to discontinue support of the FTP protocol.
Removing FTP brings us closer to a fully-secure web which is on a path to becoming HTTPS only and any modern automated upgrading mechanisms such as HSTS or also Firefox’s HTTPS-Only Mode, which automatically upgrade any connection to become secure and encrypted do not apply to FTP.