https://post.craigslist.org/manage/1340717167/tkrju#tr231033
That link will allow you to edit that post. You don't even have to be logged in.
I've already alerted them, but let's see how long this lasts.
Actually, I think craigslist probably views this more as a feature than an exploit. Since you don't need an account to post on craigslist, they can't do normal cookie based authentication, so they just give you a secret url for editing your page. Unfortunately, the only thing secret about the url is a 5 character alpha-numeric string, which I suppose would be possible to brute force.