Bait and switch. Offers downloads but any video downloaded is transparently converted, significantly lowering the bitrate while also watermarking the stream with a QR code. This code linking a site where visitors are prompted to purchase a license for the 'converter' to remove the watermark. A mark that wouldn't exist if the 'downloader' just downloaded the source without superfluous conversion. It's deceptive, invisibly inserting itself into the media in an effort to trick the gullible into believing they need a license that would, if the media wasn't converted in the first place, be unnecessary. Not to mention it appears they've got some sort of bot service periodically five-star reviewing the extension presumably to bury negative reviews.