From securityaffairs.co
On March 2nd, Microsoft released emergency out-of-band security updates that address four zero-day issues collectively tracked as ProxyLogon (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065) in all supported Microsoft Exchange versions that are actively exploited in the wild.
At the time of the release of the security patches, experts estimated that a total of 400,000 Internet-connected Microsoft Exchange servers were affected by the ProxyLogon vulnerabilities. A week later, more than 100,000 installs were still unpatched, while on March 14th, the number of unpatched servers was around 82,000.