Green / Unripe Papaya Warning!

I've been reading up like crazy -- books, websites, this app, etc. I know the no-no's of food and the try-to-avoids. But tonight for the first time ever, I was told don't eat green or unripe papaya. I couldn't believe no one had ever told me especially given how many Vietnamese and Thai restaurants serve it where I'm at. I looked it up, and sure enough, no bueno.

So I'm passing this nugget of knowledge on to all of you. I'm lucky I didn't have to make the mistake to find out, and I hope you don't either!