Do not open files in unsafe locations in Protected View
This per-user policy value controls whether Microsoft Word opens files from locations classified as unsafe in Protected View.
since 0.9.8.11
Purpose
Show registry keys (1)
HKCU\software\policies\microsoft\office\16.0\word\security\protectedview\disableunsafelocationsinpv
This per-user policy value controls whether Microsoft Word opens files from locations classified as unsafe in Protected View. Despite the policy name, it does not prevent Word from opening those files.
The value uses the REG_DWORD data type:
1: Word opens the affected files outside Protected View.0: Word opens the affected files in Protected View.- If the value is absent, the policy is not configured; files from unsafe locations open in Protected View by default.
Protected View is a read-only mode in which most editing functions are disabled. It allows users to inspect a document with reduced risk before treating it as trusted.
Notes
Security
A value of 1 removes the Protected View behavior controlled by this policy for files in unsafe locations. Those documents are consequently processed directly in normal Word mode. If a file contains malicious or manipulated content, an important protective layer is no longer present.
This value does not grant administrative privileges or general access to files. Other Word and Windows security controls—such as macro policies, File Block settings, or Office File Validation—are not automatically disabled by this setting.
Possible side effects
When the value is 0 or absent, affected documents initially have only the functionality available in Protected View. Most editing features are restricted, and add-ins may behave differently from how they operate in normal Word mode.
A value of 1 removes these functional restrictions for files that would enter Protected View solely because of their location, at the cost of the security protection described above.
Notes
Unless additional unsafe locations have been defined, the Downloaded Program Files and Temporary Internet Files folders are treated as unsafe. Administrators can classify additional folders on the local computer or network as unsafe.
The setting applies only to Microsoft Word for the current user. It controls only the unsafe-location trigger. Other reasons for using Protected View—such as Internet origin, Outlook attachments, File Block rules, or an Office File Validation failure—are not overridden by this value.
Microsoft documentation
Microsoft Support: What is Protected View?