windowscentral[.]com/windows-10-version-21h1-july-13-2021-update-many-vulnerability-fixes
Neowin is down, so there's the link to Windows Central's coverage. Of note, in one case Windows Update only showed the Malicious Software tool, and after that was installed, showed the cumulative update. While most copies of Win10 showed 4-5 updates, that was it for that copy. Also, in quite a few copies of Win10 Disk Cleanup was broken after today's updates -- Windows Update cleanup wasn't even listed. Entering this at the command prompt [under System Tools in the Start Menu for 21H1 -- or just search for cmd] **may** help:
dism /online /Cleanup-Image /StartComponentCleanup