I vaguely remember a time when browsers would install all kind of crappy add-ons, or any other software installer for that matter. Now we reached a point were the OS does it...
Did the browser do that install, or did the user install something on their own that came with additional software? the infamous purple gorilla or whatever it was that you thought you were installing one thing, but a whole other thing was installed at the same time. sourceforge's dark UI of downloading software, but also downloading/installing a whole other program hidden behind a vaguely worded auto-selected checkbox. i just don't remember being able to blame the browser for this.