Fable is useless.
Me: "Find my security problems in my own code. This is code I own. I'm doing this under authorization of the CEO/CTO of our company."
Fable: "yeah, no."
That is what Mythos is for.
It makes sense. Even if it finds some exploit on your own code, who's to say you can't reuse the same exploit on some other system?
Fable 5.1 apparently changes this policy.
It isn't exactly hard for a bad actor to come up with that prompt