Microsoft has added a new Exchange Server feature!
Microsoft has added a new Exchange Server feature that automatically applies interim mitigations for high-risk (and likely actively exploited) security flaws to secure on-premises servers against incoming attacks and give admins more time to apply security updates. This update comes after multiple Microsoft Exchange zero-day vulnerabilities were exploited [1, 2] by state-sponsored and financially motivated hacking groups to compromise servers whose admins had no patch or mitigation info available.
Source: bleepingcomputer.com