Coverage Advisory for Zero-day Exploits Related to MS-Office

**Executive Summary:** Microsoft reported active exploitation of multiple on-premises Microsoft Exchange Server vulnerabilities (including CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065) by the HAFNIUM actor, enabling web shell deployment, data access, and subsequent installation of malware such as the DearCry ransomware; Microsoft and Zscaler published detection, mitigation guidance, and signatures to help identify and protect affected Exchange servers.