A friend tells you the person your in love with has cheated in past relationships. Did I understand the question right?
I think just because someone cheated in the past doesn't mean they are necessarily going to cheat on you. Your friend might just be passing on a rumor? Or they might not know the whole situation. What if they really didn't cheat and your friend had the story wrong. Should you just drop them because of a rumor you heard?
I'd suggest getting more information from your friend if possible and then confronting the "cheater." You should be armed with some info before you confront them because if all you know is that someone said they cheated they could just deny it.
If it happens that they did cheat in the past I think it means alot if they will share with you what happened, when, who, where. I believe from there you will have a clean slate. You should emphasize that you care for them and that this cannot happen in your relationship. Hopefully, before problems get out of hand and cheating happens the two of you can talk through it to avoid the cheating or end the relationship first.
I spoke with my b/f at length regarding what happened, what to do now, and how he/we can change in the future. He said he was upset with himself because he'd allowed this to happen and almost lost me. He agreed that time, talking and positive action could heal the wounds. I told him he had to want to try to make it work, he said failure wasn't an option, it wouldn't happen again and he couldn't lose me. Well see what happens, I'm positive that we will both be giving it our best. Best to all of you too...jaz