Pressure cooked stock out overnight, still safe?
No, it is not safe.  As soon as a pressure cooker loses pressure it is not hermetically sealed. Stock, in particular, is often used as a culture medium in petri dishes to GROW bacteria.  They love the stuff.

Pressure cooking or pressure cookers do not confer magical powers to food - once the pressure is gone all the regular food handling rules apply:


Always refrigerate perishable food within 2 hours (1 hour when the temperature is above 90 °F).
When in doubt, throw it out.


Here's a little story about Bending the Rules on Bacteria and Food Safety, wherein a cookbook author feeds lethal week-old stock to his family - and the expert opinion on why this is NOT ok.