How do I confront my friend about what he knows

I was at my friend's place the other night, and I mentioned one of our mutual friends (one who I use to have a crush on). He then asks "You're bisexual, aren't you?"

I said "yeah", and he was like "It's cool, I don't mind that"
I then asked "who told you"

He then mentioned our mutual friend who he and him are close.

I didn't say anything after that. But it was a few months ago that I told our mutual friend that I liked him, and he told me that he wouldn't tell anyone.

I want to ask my other friend to see if our mutual friend told him about the crush on had on our mutual friend.

How do I kindly confront him and ask how much he knows?