Writing to file without user's confirmation

Question

I'm looking for a way to write to a file from firefox webextension addon like it was possible in old addons. I know it was removed because of security concerns but something like writing to a file inside extension's folder will be enough.

Creating a blob and asking user where to save it isn't an option due to frequent character of this writing to file.

Answer 1

Extension are no longer able to write to any file from Firefox 57+. The only option is to write data to storage and/or IndexedDB.