January 2021 Patch Tuesday is Microsoft’s first Microsoft security update release in 2021. Microsoft has released fixes for 83 vulnerabilities, with ten classified as Critical and 73 as Important. There is also one zero-day and one previously disclosed vulnerabilities fixed as part of the January 2021 updates. Microsoft also patched a publicly disclosed Microsoft splwow64 Elevation of Privilege vulnerability tracked as CVE-2021-1648. Google Project Zero previously disclosed this vulnerability in September 2020 under CVE-2020-0986.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-january-2021-patch-tuesday-fixes-83-flaws-1-zero-day/