I don't think it will work on them because they use IE to display the offers.

That won't work since it requires the installation of the Greasemonkey addon for it to work with Firefox.

^ Occurs when clicking Skip when prompted to install ShowPass

How do you plan on fixing it?

Can you please give more info regarding it?

https://arantius.com/misc/greasemonkey/script-compiler.php can convert the script that was mentioned in a previous comment to a XPI that can be added to Firefox.

Ok. Then what else would work?

Would functioning as a proxy server that unchecks the checkboxes on those sites work?

Ok. That makes sense then.

The Fissa offer is unchecked. Its still complaining that I'm going to install each of the offers that are shown when I click Next even though the checkbox/radio button is unchecked/selected which doesn't install the offer.