Rated 5 out of 5 stars

SOLUTION FOR FIREFOX 57+
Install a second version of Firefox (v.56) and deactivate the update.
Here you can find all versions:
https://ftp.mozilla.org/pub/firefox/releases/

This review is for a previous version of the add-on (5.2.0). 

Rated 3 out of 5 stars

VERY, VERY, VERY, VERY USEFUL ADD-ON!
I have thousands of MAFF-Files. This would be a disaster, if I cannot open them any more.
Please continue! Please.

This review is for a previous version of the add-on (4.1.1). 

Rated 5 out of 5 stars

Klasse! Danke!

This review is for a previous version of the add-on (3.0.0.1-signed).