Two days ago, we reported that a small number of people who installed update KB4592438 reported that Windows 10 20H2 file system gets corrupted when they run ChkDsk / f. The system will no longer boot. Microsoft has solved the problem by taking the following steps.

Microsoft: This issue is resolved and should now be prevented automatically on non-managed devices. Please note that it can take up to 24 hours for the resolution to propagate to non-managed devices. Restarting your device might help the resolution apply to your device faster. For enterprise-managed devices that have installed this update and encountered this issue, it can be resolved by installing and configuring a special Group Policy. To find out more about using Group Policies, see Group Policy Overview.

To mitigate this issue on devices which have already encountered this issue and are unable to start up, use the following steps:

  1. The device should automatically start up into the Recovery Console after failing to start up a few times.
  2. Select Advanced options.
  3. Select Command Prompt from the list of actions.
  4. Once Command Prompt opens, type: chkdsk /f
  5. Allow chkdsk to complete the scan, this can take a little while. Once it has completed, type: exit
  6. The device should now start up as expected. If it restarts into Recovery Console, select Exit and continue to Windows 10.

Note After completing these steps, the device might automatically run chkdsk again on restart. It should start up as expected once it has completed

Source: Microsoft.Support