https://www.vice.com/en_us/article/n7vpaz/researcher-publishes-code-to-exploit-microsoft-exchange-vulnerabilities-on-github

In the past couple of weeks, several hacking groups—including Chinese government hackers—have been taking advantage of four vulnerabilities to break into Microsoft Exchange email servers, used by thousands of companies all over the world. 

On Wednesday, independent security researcher Nguyen Jang published on GitHub a proof-of-concept tool to hack Microsoft Exchange servers that combined two of those vulnerabilities. Essentially, he published code that could be used to hack Microsoft customers, exploiting a bug used by Chinese government hackers—on an open-source platform owned by Microsoft.