HttpClient adds custom cookie header

I have a rather strange problem. With all these questions on the internet how to add and receive cookies, I want the opposite;)

When I try to send a request through the HttpHandler it adds its own Cookie header. I have to get rid of him. Without going into details - when it is added, the server I am trying to query gives me the wrong answer. It works without this cookie (tried fiddling).

But back to the problem, the code:

    string domain = "someMysteriousDomain";
    var handler = new HttpClientHandler();
    handler.UseDefaultCredentials = false;
    handler.AllowAutoRedirect = true;
    handler.ClientCertificateOptions = ClientCertificateOption.Manual;
    handler.UseCookies = false;

    var httpClient = new HttpClient(handler);

    var request = new HttpRequestMessage(HttpMethod.Get, domain);
    request.Headers.UserAgent.Add(new ProductInfoHeaderValue("Mozilla", "5.0"));
    request.Headers.AcceptEncoding.Add(new StringWithQualityHeaderValue("gzip"));

    var response = await httpClient.SendAsync(request);

      

        
        
        
      

    

The unhandled request seen in the fiddler:

GET https://domain HTTP/1.1
Accept-Encoding: gzip
User-Agent: Mozilla/5.0
Host: domain
Connection: Keep-Alive
Cookie: cadata477E7C1824F44800AF0077724F65345="51595d316-0286-44bb-bc6f-ffb1fd311a92SqJA36rA69YW7aBg+iHXYi9LAcBLN6DBWE8a3MLejd2VCluO/UQ5eF6F6T4NWh4NhdRcv4rea15Hs0e2q6GatMac59UVbljhREYdH6PRbzZC/2qn8QHtpc6go5B56R"; mobile=0

      

        
        
        
      

    

I don't want to add this cookie! How do I uninstall / clear / whatever? I am using Visual Studio Community 2015 with Windows Universal Project. Interestingly, after restarting my computer after a few hours, I was able to make 2 or 3 requests without this cookie (using the THEOREM code) and then mysticios cookie returned. What is it about? How to get rid of it?