How to find out if a user is an administrator?

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Hello.
So, for experience, let's say, an application for Vkontakte groups, and there is such a problem, you need to identify the user, whether he is an administrator, VK transmits GET parameters when loading the application (viewer_type tells us the user's rights level), but it's worth editing the iframe address a little, and the script considers us to be an administrator, the access_token that is passed when the application is loaded can only be used from the user's IP), and it does not occur to me how to solve this problem.
The level of rights must be checked on the server side.
Tell me please.