The Microsoft security updates for May 2021 have been released. They consist of 55 Common Vulnerabilities and Exposures (CVEs):
4 are rated Critical
1 is rated Moderate in severity.
Although three of the bugs are listed as being publicly known, none are listed as currently being exploited.
For more information please see THE MAY 2021 SECURITY UPDATE REVIEW by Dustin Childs https://www.zerodayinitiative.com/blog/2021/5/11/the-may-2021-security-update-review