Fix to make it work Rated 4 out of 5 stars
Love this extension & use it all the time. Here's how to fix it to work with the latest versions of FF. Download + open the .xpi in an app like 7zip.. extract the .jar, open the .jar in 7zip and edit dragdropupload.js (in content). Go to line 844 and comment out the alert.
Save the changes, add the .jar back into the .xpi and drop it onto FF to install it.
Now I don't get the error when I drop a file into FF & it works fine.