There is an extension/add-on for Firefox called Video Download Helper that lets users download embedded videos from all sorts of websites. While it works as a simple Firefox add-on sometimes, for a remarkable portion of sites (e.g. on Vimeo) it says that it cannot do so as installed and states that the user has to install the companion app to their computer. Does anyone know if this is safe or is installing it placing myself in any risk? If you suggest against installing the companion app, do you have any other recommendations on how to download videos embedded videos from websites?

Edit: I’m on a Debian-derivative distro.