To me KISS is basically about how you’d write the code, the architecture, which is something that - at least currently - humans need to oversee when writing new code with LLMs.
But what does it have to do with AI discovering a ton of bugs in a lot of (open-source) software?
Someone not following KISS, might install Windows Server + tons of bloated applications, in order to serve a .asp server, which serves JSON that never changes, or something similarly stupid.
Meanwhile, the KISS developer would put static .json files on a CDN or self-hosted Varnish or whatever, and call it a day.
The first opened up a whole can of potential venues for exploitation, while the second might only have opened up one potential venue for exploitation.
Maybe, when they build a pomodoro timer, people will consider the possibility that the entirety of a browser engine as well as 30 000 javascript dependencies from random unvetted sources introduces unnecessary complexity and a practically infinitely fractal attack surface.