You never really imagined it to happen this way, but suddenly you're contemplating if you should really go on a date with your new catch, since you're catch is your friends ex.
Most people will say, and I will have to agree, friends exes are OFF LIMITS. It doesn't matter if they dated for 10 days or 10 years, there was once some romantic attraction. If their relationship ended badly, your new beginning with your new date may have your friendship ending badly as well.
First off, if you need to establish how interested in this person you really are. If it plays out for a few weeks and you don't see it going far then it seems to be all fun and games. However, you need to think of how your friend would feel about you dating their ex, no matter how casually you are dating them. Think of how you would feel if you were in their position, and DON'T make excuses about how they were never meant to be and how she broke up with him and so on...
An
article on SeatlePi.com states a rule," In a way, you need the 24k golden rule, and not just the 14k -- you can't decide based on what's right for this or that individual, but on what serves a larger idea of Right."
Basically, in order for it to be okay, it needs to be okay from 360'. Everyone needs to know the truth, and all parties must approve. If the friend is honestly okay with it, then happy dating!
If the friend is not okay with it, or really dislikes their ex, your friendship may get a bit rocky.
Your best bet would be to find someone who has no strings attached to anyone you really care about. Find someone completely eligible to be called your new fling.