Information
This feature configures whether a user is warned before opening an external application for pre-configured protocols were its behavior is undefined.
Rationale:
Enabling a warning to appear before passing data to an external application mitigates the risk that sensitive information will be made vulnerable to outside threats.
Impact:
None - This is the default behavior.
Solution
To establish the recommended configuration, set network.protocol-handler.warn-external-default to true:
Type about:config in the address bar
Type network.protocol-handler.warn-external-default in the filter
Ensure the setting is set as prescribed.
OR
Open the mozilla.cfg file in the installation directory with a text editor
Add the following lines to mozilla.cfg:
lockPref('network.protocol-handler.warn-external-default', true);
Default Value:
True