Adobe Reader DC must disable the ability to change the Default Handler.

Allowing user to make changes to an application case cause a security risk.

When the Default PDF Handler is disabled, the end users will not be able to change the default PDF viewer.

Verify the following registry configuration:

Utilizing the Registry Editor, navigate to the following: HKEY_LOCAL_MACHINE\Software\Policies\Adobe\Acrobat Reader\DC\FeatureLockDown

Value Name: bDisablePDFHandlerSwitching Type: REG_DWORD Value: 1

If the value for bDisablePDFHandlerSwitching is not set to “1” and Type configured to REG_DWORD or does not exist, then this is a finding.

Configure the following registry value:

Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \Software\Policies\Adobe\Acrobat Reader\DC\FeatureLockDown

Value Name: bDisablePDFHandlerSwitching Type: REG_DWORD Value: 1