Mozilla has decided to remove the built-in FTP protocol implementation from Firefox. In the upcoming Firefox 88, scheduled for April 19, FTP support will be disabled by default (including the setting browserSettings.ftpProtocolEnabled, which will be set to read-only), and in Firefox 90, planned for June 29, the code related to FTP will be removed. When trying to open links with the protocol identifier "ftp://", the browser will invoke an external application, similar to how it invokes handlers for "irc://" and "tg://".
The reason given for discontinuing FTP support is the protocol's vulnerability to modification and interception of transit traffic during MITM attacks. According to Firefox developers, there is no reason to use FTP instead of HTTPS for resource downloads in modern conditions. Additionally, the code supporting FTP in Firefox is very old, creates maintenance issues, and has a history of several vulnerabilities in the past.
It should be noted that in Firefox 61, resource downloading via the FTP protocol from pages opened over HTTP/HTTPS was already prohibited, and in Firefox 70, rendering of files downloaded through FTP was stopped (for example, images, README, and HTML files stopped displaying when opened via FTP and the file download dialog was shown immediately instead). In Chrome, FTP support was discontinued in the January release of Chrome 88. According to Google's estimates, FTP is hardly used anymore—FTP user share is about 0.1%.
Source: opennet.ru
