Doesn't seem to actually do anything. You go to a website, you get a pop-up that says "get 0.2% cash back!" you click to confirm, and then nothing else really happens. I've made dozens of purchases, and I just now checked my all-time cash back: $0.00.

Also if you're browsing amazon, you get this little pop-up that's basically like "this was made in china" and I'm like "...yeah. thanks."

The dev vehemently denies that it harvests your data but it literally says "Store unlimited amount of client-side data" and
"Access your data for all web sites" right on the permissions panel. So it doesn't take a genius to figure out that this free app is literally just a data harvesting tool.