http://twd6bfktlkhwluhj2ghjthx55pnp2dcuuhf6qqjz7vm2krsmwpz6crad.onion/the-great-leak-microsoft-exchange-autodiscover-design-flaw/index.html
According to Amit Serper , the person who discovered the flaw, the source of the leak is comprised of two issues; the design of the Autodiscover protocol, more specifically the “back-off” algorithm, and the poor implementation of the protocol in some applications.