Vk.api getProfiles/users.get started returning hidden parameter - what is it?

Question

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Today, one of my VK applications stopped working normally (I won’t name them - I don’t want advertising).
The essence of the problem: the answer to the request, a la:

http://api.vk.com/api.php?api_id=****&fields=uid, ****, online,&format=json&method=getProfiles&random=5673&uids=****&v=3.0&sig=b******a

answer:

{"response":[{"uid":****, ***, <b>"hidden":1</b>, "online":0}]}

What is hidden ? Who knows? (search on the documentation and Google did not give a result).
More interestingly, if it returns hidden=1, then online=0 is always (even if the site actually has a mark on the page that it is online).
But the most interesting thing is that not all users have hidden=1, in some they do not return it at all. and then online=0 or 1
I immediately thought about the privacy settings or something else - I experimented and nothing has changed.
Who can shed some light on this?
// iFrame application, the cron server makes requests to api
// I see that api has changed a lot since the development of the application (year 3), maybe I missed something? Some kind of authorization?

Answer 1

hidden=1 - returns when setting the user's privacy for displaying the page "only to VK users"

Answer 2

In the same place, in my opinion, you can hide a few friends. Can for them and returns this value?
PS: Isn't it better to ask the support service?