better to stay out of it, it's just going to look like you are trying to break them up. Let his best friend tell him.
but you still need to respect his bounderies and that isn't.
If he is your "ex," that is supposed to mean that you two no longer are intimately involved. So I assume that passing along some destructive info about the ex's new girlfriend would not be appropriate or helpful. Get on with your own life and let him live his.
It could be a set up. I would not say anything unless you and your ex are on excellent terms.
Too much drama, stay out of it and mind your own business
to many XXXX's