Восстановил авторизацию через логин/пароль

VkNet.Tests/Categories/Users/UsersCategoryTest.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -560,7 +560,7 @@ public void Get_NotAccessToInternet_ThrowVkApiException()
 	{
 		Mock.Get(Api.RestClient)
 			.Setup(f =>
-				f.PostAsync(It.IsAny<Uri>(), It.IsAny<IEnumerable<KeyValuePair<string, string>>>(), Encoding.UTF8))
+				f.PostAsync(It.IsAny<Uri>(), It.IsAny<IEnumerable<KeyValuePair<string, string>>>(), Encoding.UTF8, null))
 			.Throws(new VkApiException("The remote name could not be resolved: 'api.vk.com'"));
 
 		FluentActions.Invoking(() => Api.Users.Get(new long[]

VkNet.Tests/Infrastructure/BaseTest.cs

@@ -89,7 +89,7 @@ public BaseTest()
 		Mocker.Setup<IRestClient, Task<HttpResponse<string>>>(x =>
 				x.PostAsync(It.Is<Uri>(s => s == new Uri(Url)),
 					It.IsAny<IEnumerable<KeyValuePair<string, string>>>(),
-					It.IsAny<Encoding>()))
+					It.IsAny<Encoding>(), null))
 			.Callback(Callback)
 			.Returns(() =>
 			{
@@ -103,7 +103,7 @@ public BaseTest()
 
 		Mocker.Setup<IRestClient, Task<HttpResponse<string>>>(x => x.PostAsync(It.Is<Uri>(s => string.IsNullOrWhiteSpace(Url)),
 				It.IsAny<IEnumerable<KeyValuePair<string, string>>>(),
-				It.IsAny<Encoding>()))
+				It.IsAny<Encoding>(), null))
 			.Throws<ArgumentException>();
 
 		Api = Mocker.CreateInstance<VkApi>();

VkNet/Abstractions/Utils/IRestClient.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Net;
 using System.Text;
@@ -40,6 +40,7 @@ public interface IRestClient : IDisposable
 	/// <param name="uri"> Uri </param>
 	/// <param name="parameters"> Параметры </param>
 	/// <param name="encoding"></param>
+	/// <param name="headers"> Заголовки </param>
 	/// <returns> Строковый результат </returns>
-	Task<HttpResponse<string>> PostAsync(Uri uri, IEnumerable<KeyValuePair<string, string>> parameters, Encoding encoding);
+	Task<HttpResponse<string>> PostAsync(Uri uri, IEnumerable<KeyValuePair<string, string>> parameters, Encoding encoding, IEnumerable<KeyValuePair<string, string>> headers = null);
 }

VkNet/Infrastructure/Authorization/ImplicitFlow/Forms/AbstractAuthorizationForm.cs

@@ -32,7 +32,7 @@ public async Task<AuthorizationFormResult> ExecuteAsync(Uri url, IApiAuthParams
 
 		FillFormFields(form, authParams);
 
-		var response = await _restClient.PostAsync(new(form.Action), form.Fields, Encoding.GetEncoding(1251))
+		var response = await _restClient.PostAsync(new(form.Action), form.Fields, Encoding.UTF8, form.Headers)
 			.ConfigureAwait(false);
 
 		if (!response.IsSuccess)

VkNet/Infrastructure/Authorization/ImplicitFlow/Forms/ImplicitFlowLoginForm.cs

@@ -29,5 +29,12 @@ protected override void FillFormFields(VkHtmlFormResult form, IApiAuthParams aut
 		{
 			form.Fields[AuthorizationFormFields.Password] = authParams.Password;
 		}
+
+		form.Headers = new System.Collections.Generic.Dictionary<string, string>
+		{
+			{ "content-type", "application/x-www-form-urlencoded" },
+			{ "origin", "https://oauth.vk.com" },
+			{ "referer", "https://oauth.vk.com/" }
+		};
 	}
 }

VkNet/Infrastructure/Authorization/ImplicitFlow/VkHtmlFormResult.cs

@@ -26,4 +26,9 @@ public class VkHtmlFormResult
 	/// Поля формы
 	/// </summary>
 	public Dictionary<string, string> Fields { get; set; }
+
+	/// <summary>
+	/// Заголовки для запросов
+	/// </summary>
+	public Dictionary<string, string> Headers { get; set; }
 }

VkNet/Utils/RestClient.cs

@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Net;
 using System.Net.Http;
+using System.Net.Http.Headers;
 using System.Text;
 using System.Threading.Tasks;
 using JetBrains.Annotations;
@@ -50,14 +51,27 @@ public Task<HttpResponse<string>> GetAsync(Uri uri, IEnumerable<KeyValuePair<str
 	}
 
 	/// <inheritdoc />
-	public Task<HttpResponse<string>> PostAsync(Uri uri, IEnumerable<KeyValuePair<string, string>> parameters, Encoding encoding)
+	public Task<HttpResponse<string>> PostAsync(Uri uri, IEnumerable<KeyValuePair<string, string>> parameters, Encoding encoding, IEnumerable<KeyValuePair<string, string>> headers = null)
 	{
 		if (_logger != null)
 		{
 			var json = JsonConvert.SerializeObject(parameters);
 			_logger.LogDebug("POST request: {Uri}{NewLine}{PrettyJson}", uri, Environment.NewLine, Utilities.PrettyPrintJson(json));
 		}
 
+		if (headers != null && headers.Any())
+		{
+			headers.ToList().ForEach(header => {
+				if (header.Key.ToLower() == "content-type")
+				{
+					HttpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(header.Value));
+				} else
+				{
+					HttpClient.DefaultRequestHeaders.Add(header.Key, header.Value);
+				}
+			});
+		}
+
 		var content = new FormUrlEncodedContent(parameters);
 
 		return CallAsync(() => HttpClient.PostAsync(uri, content), encoding);