another random user writes "Skype vulnerability allowing hijacking of any account if you know just the email address.
All you need to do is register a new account using that email address, and even though that address is already used (and the registration process does tell you this) you can still complete the new account process and then sign in using that account.
Apologies in advance for the following reddit link, but it may be easier for some to read than the original Russian page.
Info about this on reddit, original post in Russian"
Link to Original Source