I made chinese donuts which has flour, water, sugar, alum, salt, baking
powder, baking soda, and some oil on top to keep it moist. I put it in
a ziplock bag, all sealed up. And there's no yeast whatsoever in
this...

I left it in a cool spot (not the fridge) for a day and black dots
starts appearing in the dough.

Can someone please explain why this is? And how long can dough like
this last for before going bad?

Thanks!
Dawn