Cake baking with buttercream

[nameisnotimportant]

I don't know if I've put this in the right section but I made buttercream icing on Saturday and put the leftovers in the fridge in an airtight container. I want to use it tonight to decorate some cupcakes. Once decorated, do I need to put the cupcakes into the fridge or can they sit out until we eat them tomorrow ? I have Googled it and can't seem to find the answer anywhere 🤷🏼‍♀️

You can leave them out. Buttercream has so much sugar that it acts like a preservative. You could put them in a Tupperware box just to stop the cake drying out but no need to refrigerate.

Yup, they can be left out. The only risk is of it melting if it is super hot where you are.