> You need root in order to overwrite sudo in the first place I think

You just need write access to .bashrc or similar.

> This is why I think it is a good idea to get a yubikey and use PAM to require a physical user presence check to acquire root privileges.

Unprivileged malware will be waiting with a root payload ready to fire the next time you tap your yubikey.

Look at the excerpt. They're not overwriting the sudo binary. The attack vector is real for malware running on a administrator user session which can be escalated to root via sudo.

It's a niche, but it's real. Esp. if you're targeting npm installed user scripts or similar

No, the above attack writes that function into bashrc, meaning the next time the user runs sudo themselves, you harvest their password.

You do not need root to run that shell function, nor to get it loaded into a shell's environment.

They didn't say anything about overwriting the sudo binary, and that is not required, which I think was their whole point was to show exactly how that is not required.