Source: https://msrc-blog.microsoft.com/blog/2021/04/april-2021-update-tuesday-packages-now-available/
Update August 25, 2021:
Microsoft strongly recommends that you update your servers with the most recent security updates available.
CVE-2021-34473 (ProxyShell) CVE-2021-34523 (ProxyShell) CVE-2021-33766 Today is Update Tuesday – our commitment to provide a predictable monthly schedule to release updates and provide the latest protection to our customers. Update Tuesday is a monthly cycle when Microsoft releases patches for vulnerabilities that we have found proactively or that have been disclosed to us through our security partnerships under a coordinated vulnerability disclosure.
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