Microsoft Exchange Server Remote Code Execution Vulnerability
https://www.zscaler.com/blogs/security-research/retrospective-avoslocker
https://www.tenable.com/cyber-exposure/2021-threat-landscape-retrospective
https://www.zerodayinitiative.com/advisories/ZDI-21-821/
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473