The Firefox platform development team recently announced plans to first disable, and then remove the implementation for built-in FTP from the browser. FTP is a protocol to transfer files from one host to another. It predates the Web and was not designed with security in mind. Now, we have decided to remove it because it is an infrequently used and insecure protocol. After FTP is disabled in Firefox, people can still use it to download resources if they really want to, but the protocol will be handled by whatever external application is supported on their platform.
FTP was disabled on the Firefox Nightly pre-release channel on April 9. To mitigate the risk of potentially causing breakages during the COVID-19 pandemic, FTP will not be disabled from the Firefox release channel until at least July 2020. If the pandemic situation has not improved by July 28 (the expected release date for Firefox 79), there may be further delays.
Add-ons that use FTP may experience breakage on Nightly but will continue to work as usual on the Beta and release channels. We want to help developers address these breakages as best as we can while this change is on Nightly. If you maintain an extension that uses FTP, please test it on Nightly (or on any current version of Firefox by flipping the preference
network.ftp.enabled to false) and file a bug if you notice any issues. We will also evaluate whether new features should be added to help you maintain file transfer functionality.
In the long-term, we encourage developers to move away from using FTP in their extensions. However, if you would like to continue using FTP for as long as it is enabled, we encourage you to wrap any features that require FTP and use the browserSettings API to check whether FTP is enabled before exposing that functionality.
Please let us know if there are any questions on our developer community forum.