Okay, so I'm not entirely sure if this is a me problem or a book problem.
I think the spell Harm is missing a 'Defense' entry in the stat block before the spell's description. I took a quick look at some other spells, and that entry seems normal for damaging spells that don't require an attack roll, like Falling Stars, Fireball, Frostbite, Lightning Bolt, etc.
Harm doesn't have that entry. It *does* mention a Fortitude save in the text of the spell, though. Funnily enough it uses language near-identical to Frostbite, which lists 'Defense: Fortitude' before the description. So, for consistency's sake, I think Harm ought to have it as well.
The only thing giving me pause is, it was like this in the 2E Pathfinder CRB as well. So maybe there's a reason I'm missing?