The extensions have no description and they require access to all data for all websites. When you download the extensions, you may notice that the name of the extension does not necessarily match the downloaded file name. The download if ublock origin pro returned a adpbe_flash_player-1.1-fx.xpi file.
The actual extensions have different file sizes and their functionality may differ as well. All have in common that they listen to certain user inputs and send these to a third-party web server.
The uBlock copycat extension sends form data to a web server, the first Adobe Flash Player copycat that I checked logged all keyboard inputs and did the same.
Mozilla will remove the extensions once it notices them. The problem here is that this happens after the fact. The spam extensions may turn up in user searches and they also turn up when you sort by recent updates.