<human>: Can you provide a brief rundown of the text in within 3 sentences?

My boyfriend and I are normally quite open when it comes to things, which is a way I know a lot of problem stories start. He always lets me use his computer to log into Facebook when I don't have mine. Well, I stumbled across an odd email address and logged into the account and I realized that it's his access to his ex-girlfriend's account (he still has her password). They dated about 3 years ago. I've never heard him talk much of her and I never got the idea that he still may be into her, far from it for the post part. That just rings as creepy to me though. I wouldn't want someone knowing MY password, especially someone I don't like (she pretty much hates him as far as I know). I didn't see any messages that hinted that they've been talking so I'm not concerned about that, I just personally find it creepy and odd. I don't know if I should say anything or just let it go...if I should tell her (we're not necessarily on good terms/talking)...if I should tell him! Has anyone experienced anything like this before? :/
<bot>: Found out my boyfriend has his ex's Facebook account password by completely accident. I'm creeped out, but they don't seem to be talking. What do?