I have absolutely no clue what you are talking about. There is no mechanism in standard Linux distributions to automatically download software from a vendor when you plug a device (apart from firmware updates through fwupd, but those are curated).
So perhaps you could elaborate?
> no mechanism in standard Linux distributions
Now, when I first ran Linux in the mid-1990s, this was true. "Plug-and-play" is just peaking over the horizon. Other systems have had it for years (the Amigans for example) but for the PC it's pretty new.
But today a whole lot of mechanism is spun up when the kernel realises something new was added. A netlink socket talks to a udev daemon, in userspace and that daemon, being ordinary userspace software can do whatever it wants including of course run a bunch of arbitrary shell scripts, which can in turn do whatever they want. So yes of course they could download arbitrary software, or delete all your files with a Z in their name.
> from a vendor
Where the Adware comes from is of no consequence to the end user. "Um actually, the file came from Microsoft's servers" is irrelevant.
[Speaking more specifically of fwupd, which is ultimately fed by hardware vendors directly]
> but those are curated
I'm sure Microsoft considers that they are curating their system too. We both just think (I assume you're not here to defend Microsoft) their curation sucks.
I want to be sure we're pointing at the right thing here. The problem isn't that your Windows PC can end up running software because a device was plugged in, that's actually convenient and a benefit to many people and that works in Linux. The problem is what was delivered.