A memory corruption vulnerability exists when Windows Media Foundation improperly handles objects in memory. An attacker who successfully exploited the vulnerability could install programs; view, change, or delete data; or create new accounts with full user rights. There are multiple ways an attacker could exploit the vulnerability, such as by convincing a user to open a specially crafted document, or by convincing a user to visit a malicious webpage. The security update addresses the vulnerability by correcting how Windows Media Foundation handles objects in memory.
https://www.tenable.com/blog/microsoft-s-august-2020-patch-tuesday-addresses-120-cves-cve-2020-1337
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1492