This didn't work at all for me. I visited a website supported by Faircado (Amazon), go to a product page, get the green square thingy in the upper right corner, click it, and get redirected to a website that is probably supposed to show me search results, but only shows a website with a search mask and product categories I can search for (which in my test case, a book, was completely useless). I got the same problems with other products (headphones, for example).

I guess this might be some kind of redirection issue, but this addon gives zero feedback in that regard, and just fails silently. Add to that that there is no support site (just the homepage, again), and I don't even care enough anymore to find out how to report this possible bug.