The "v" parameter with version number becomes obligatory for all API …

src/Owin.Security.Providers.VKontakte/Provider/VKontakteAuthenticatedContext.cs

@@ -25,7 +25,7 @@ public VKontakteAuthenticatedContext(IOwinContext context, JObject user, string
             User = user;
             AccessToken = accessToken;
 
-            Id = TryGetValue(user, "uid");
+            Id = TryGetValue(user, "id");
             var firstName = TryGetValue(user, "first_name");
             var lastName = TryGetValue(user, "last_name");
             UserName = firstName + " " + lastName;

src/Owin.Security.Providers.VKontakte/VKontakteAuthenticationHandler.cs

@@ -61,7 +61,7 @@ protected override Task ApplyResponseChallengeAsync()
             var state = Options.StateDataFormat.Protect(properties);
 
             var authorizationEndpoint =
-                $"{Options.Endpoints.AuthorizationEndpoint}?client_id={Uri.EscapeDataString(Options.ClientId)}&redirect_uri={Uri.EscapeDataString(redirectUri)}&scope={Uri.EscapeDataString(scope)}&state={Uri.EscapeDataString(state)}&display={Uri.EscapeDataString(Options.Display)}";
+                $"{Options.Endpoints.AuthorizationEndpoint}?client_id={Uri.EscapeDataString(Options.ClientId)}&redirect_uri={Uri.EscapeDataString(redirectUri)}&scope={Uri.EscapeDataString(scope)}&state={Uri.EscapeDataString(state)}&display={Uri.EscapeDataString(Options.Display)}&v={Uri.EscapeDataString(Options.ApiVersion)}";
 
             Response.Redirect(authorizationEndpoint);
 
@@ -156,7 +156,7 @@ private async Task<JObject> GetUser(JObject response, string accessToken)
 
             // Get the VK user
             var userRequestUri = new Uri(
-                $"{Options.Endpoints.UserInfoEndpoint}?access_token={Uri.EscapeDataString(accessToken)}&user_id{userId}");
+                $"{Options.Endpoints.UserInfoEndpoint}?access_token={Uri.EscapeDataString(accessToken)}&user_id{userId}&v={Uri.EscapeDataString(Options.ApiVersion)}");
             var userResponse = await _httpClient.GetAsync(userRequestUri, Request.CallCancelled);
             userResponse.EnsureSuccessStatusCode();
 

src/Owin.Security.Providers.VKontakte/VKontakteAuthenticationOptions.cs

@@ -14,6 +14,7 @@ public class VKontakteAuthenticationOptions : AuthenticationOptions
         private const string UserInfoEndpoint = "https://api.vk.com/method/users.get";
         private const string DefaultCallbackPath = "/signin-vkontakte";
         private const string DefaultDisplayMode = "page";
+	    private const string DefaultApiVersion = "5.73";
 
         /// <summary>
         ///     Gets or sets the a pinned certificate validator to use to validate the endpoints used
@@ -100,10 +101,18 @@ public string Caption
         /// </summary>
         public ISecureDataFormat<AuthenticationProperties> StateDataFormat { get; set; }
 
-        /// <summary>
-        ///     Initializes a new <see cref="VKontakteAuthenticationOptions" />
-        /// </summary>
-        public VKontakteAuthenticationOptions()
+	    /// <summary>
+	    /// Default API version. Required.
+	    /// </summary>
+	    /// <remarks>
+	    /// Defaults to 5.73
+	    /// </remarks>
+	    public string ApiVersion { get; set; }
+
+		/// <summary>
+		///     Initializes a new <see cref="VKontakteAuthenticationOptions" />
+		/// </summary>
+		public VKontakteAuthenticationOptions()
             : base(Constants.DefaultAuthenticationType)
         {
             Caption = Constants.DefaultAuthenticationType;
@@ -118,6 +127,7 @@ public VKontakteAuthenticationOptions()
                 TokenEndpoint = TokenEndpoint,
                 UserInfoEndpoint = UserInfoEndpoint
             };
+	        ApiVersion = DefaultApiVersion;
         }
     }
 }