This thread is resolved. Here is a description of the problem and solution.
Problem:
The issue here is that the user wanted to know if a custom field data is available if its not being displayed on the page.
Solution:
No if the custom field isn't added to a template that displays the data then the frontend users won't be able to know what is the value of that custom field.
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For example, if I create a custom field and only display them on a private, or password protected page, are they visible anywhere else? Can the data be extracted from a post?
What about if these fields are used on a public page? Can the date be extracted in any way then if they are not set to display using shortcodes or anything similar?
If the field isn't being displayed then no it cannot be extracted.
If you hide the fields using our Access shortcodes then no they won't accessible. So long as the content is physically on the page then its not accessible to the users from the frontend.
So just to confirm, if I have a custom field that is not included in search results, and not displayed on the front end anywhere, then the information stored for each post in this field is not visible to anyone without back end access?
If you didn't add the shortcode to display the information on the page, then they wont have access to it. Only the information that you set to display they will have access to.