From the edition Firefox 77, the connection function in FTP servers will be disabled, but the user is interested will be able to reactivate it with the network option.ftp.enabled to internal URL about: config. This will not affect the ESR versions where the connection to FTP servers will remain operational at least until version 78.
For 2021, Mozilla plans to remove all of its code FTP from its browser, for the following reasons:
- The protocol FTP is obsolete.
- The code FTP existing in the browser is also outdated and difficult to maintain in modern versions of the browser.
- Links to FTP (not in sFTP) are insecure in MITM (man-in-the-middle) attacks.
As you may remember that from him Firefox 61 Mozilla browser does not load resources FTP websites, e.g. images, which have links from FTPs. Starting from the version Firefox 70, the browser does not render the files in FTP.
According to Google statistics, only 0,1% of Chrome users use FTP.