Last week I did some cupcakes which not only rose but they also spread out wide. I filled it 2/3 full but still some overflowed. The ones that haven't overflowed still were wide. If I were to put these in a fancy cupcake case afterwards, how would I fit it in? How can I overcome this problem? Do I need to add more flour?

Fist i would try turning up the heat in your oven. So that the cup cakes have less time to spread. I don't really understand how the cup cakes could get wide if they hadn't overflowed the pan. But the heat is what i would try first. I do figure that you like the cake recipe that you are using already and if you add more flour to it, you will change the recipe and probably won't be happy.

Ditto what peg818 said.

By saying your cupcakes widened, it must be that the rose over the top of the pan and were like muffin tops, not the whole cupcake got wider.

This is from not having a hot enough oven. Without the right heat instead of raising up and doming, they will rise and spread, thus getting wider at the top than the paper.

Is this a scratch recipe or box?

This was from a scratch recipe. The case acutally started to widen while I was filling in the cases (before they were put in the oven), once in the oven, they got worse. Its as if the cases were not secure enough

Did you use a muffin pan?

It sounds like you tried to make them using cupcake liners without a muffin pan? The only way you can do that is if you use foil liners, or ones advertised to be used without a pan.

Yes, I didn't use a muffin tin, just used the paper liners. Maybe I should invest in a muffin tin then.

yes you need a muffin tin.