Do not open files from the Internet zone in Protected View
since 0.9.8.11
Purpose
Show registry keys (1)
HKCU\software\policies\microsoft\office\16.0\excel\security\protectedview\disableinternetfilesinpv
This per-user REG_DWORD value controls whether Excel opens files from the Internet zone in Protected View.
When set to 1, qualifying files bypass Protected View and open in the normal Excel environment. When set to 0, they open in Protected View for this trigger. Excel identifies Internet-zone files through stored zone information, commonly referred to as the Mark of the Web.
Protected View is a read-only mode in which most editing functions are disabled. Enabling disableinternetfilesinpv removes that protection for files that would otherwise enter Protected View because they are associated with the Internet zone.
Notes
Additional effects
Affected workbooks are immediately available in the normal editing environment. Protected View restrictions on active content, including VBA macros and data connections, do not apply to that opening session.
The value does not override independent security policies. Macros, ActiveX controls, external content, and other active components remain subject to the applicable Trust Center and policy settings. It also does not generally disable Protected View when another condition applies, such as a failed Office File Validation check or a policy covering unsafe locations.
Security
Setting the value to 1 removes Protected View specifically from files that Windows or Excel has classified as originating from the Internet zone. A malicious workbook is therefore processed outside the restricted, read-only environment, increasing the risk that an Excel vulnerability could be exploited or that a user could edit or activate harmful content.
This value does not automatically enable macros or all other active content. Separate macro and content-security policies continue to determine whether such content may run. Nevertheless, bypassing Protected View removes an additional security layer that prevents editing and restricts active content.
Possible side effects
Workbooks obtained from the Internet open without the read-only preview state associated with that origin. Users can modify them immediately, and the Protected View warning and deliberate transition to editing are omitted.
Notes
The setting applies per user and specifically to Excel applications that use the Office 16.0 registry branch. It affects only files that Excel recognizes as originating from the Internet zone. If usable zone information is absent or has been removed, the file's origin cannot be evaluated through this mechanism.
Microsoft documentation
Microsoft Support: What is Protected View?