Rated 5 out of 5 stars

it does not work on Firefox 57. I had to install Copy On Select https://addons.mozilla.org/en-GB/firefox/addon/copy-on-select/
But, thanks for your efforts. It used to work great and I hope you will fix it because I am worried about one of the permissions of Copy On Select: "Access your data for all websites". So, 5 stars for the good work when it worked.

Rated 5 out of 5 stars

It works great. The middle click pasting can be turned on in the prog's settings.