I once came up with a silly way of hijacking facebook accounts that were registered with @hotmail.com. I told both facebook and microsoft about this, never got even a thank you. I know that are some people who make a living out of bug bounty, but I felt very discouraged back then (I was still in college) and never bothered to try again.
Write about it! I’m sure somebody would appreciate reading it.
Later came Facebook and people created their account using the @hotmail.com and starting to left MSN, since facebook had a messenger. One day I received an email from Microsoft saying that they were disabling MSN (I'm telling this from memory, forgive me if I'm saying anything super wrong).
Fast forward to me being in college and studying a little bit of pentest. As I recall I was trying to see how much information a could gather from a person by their facebook page (as a non friend). If you try to login using their ID (or username) you could find pieces of cellphone number and emails. So I tried this with a profile from some girl I had a crush back in the day and discovered that shed used MSN as email.
Eventually I tried to log in her email on MSN and found out it has been disabled for a while. So I tried to recreate the email account with me as the owner and for my surprise it worked. I then went back to facebook and recover "my" password. With the email and password, facebook didn't let me login because of my location. But I knew where this girl lives, so I found a proxy server [1] and bam, I was in.
Not going to lie, I did look at some of her messages and pictures, but felt very bad after and decided to tell facebook and microsoft about it. This was facebook's response [2]. After a day or two of getting no answers from both companies (before I got the answer from facebook), I told the story to about 2 or 3 tech reporters. They told me they wrote to microsoft asking for a comment, but never got any answer. A week later I tried to recreate another "dead" account on hotmail and I couldn't. Don't remember exactly what they did, but I just couldn't create the email, so I figure they has fixed it.
1 - http://free-proxy.cz/en/proxylist/country/BR/all/ping/all 2 - https://imgur.com/a/kFMlO6d