This is an interesting way to try to get folks to open malicious documents. I really like the macro warning screen angle they use on this. It’s designed to get you to click the button to enable the macro when it’s opened. They also make the email look like you are being brought in to an existing conversation. Pretty slick.
Check it all out at: https://blog.knowbe4.com/phishing-from-the-middle-social-engineering-refined