diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/InternalAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/InternalAPI.Unshipped.txt
index 74f7de658..d6de268e9 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/InternalAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/InternalAPI.Unshipped.txt
@@ -2,5 +2,6 @@
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.get -> string?
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.set -> void
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForApp(Microsoft.Identity.Client.AcquireTokenForClientParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForTestUser(Microsoft.Identity.Client.AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
 readonly Microsoft.Identity.Web.TokenAcquisition.tokenAcquisitionExtensionOptionsMonitor -> Microsoft.Extensions.Options.IOptionsMonitor<Microsoft.Identity.Web.TokenAcquisitionExtensionOptions!>?
 static Microsoft.Identity.Web.TokenAcquisition.ResolveTenant(string? tenant, Microsoft.Identity.Web.MergedOptions! mergedOptions) -> string?
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/PublicAPI.Unshipped.txt
index d1805fb40..68eb4d560 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net462/PublicAPI.Unshipped.txt
@@ -2,6 +2,8 @@
 const Microsoft.Identity.Web.ClaimConstants.Password = "xms_password" -> string!
 const Microsoft.Identity.Web.ClaimConstants.Username = "xms_username" -> string!
 Microsoft.Identity.Web.BeforeTokenAcquisitionForApp
+Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForApp -> Microsoft.Identity.Web.BeforeTokenAcquisitionForApp?
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForTestUser -> Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser?
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.TokenAcquisitionExtensionOptions() -> void
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/InternalAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/InternalAPI.Unshipped.txt
index 74f7de658..d6de268e9 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/InternalAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/InternalAPI.Unshipped.txt
@@ -2,5 +2,6 @@
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.get -> string?
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.set -> void
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForApp(Microsoft.Identity.Client.AcquireTokenForClientParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForTestUser(Microsoft.Identity.Client.AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
 readonly Microsoft.Identity.Web.TokenAcquisition.tokenAcquisitionExtensionOptionsMonitor -> Microsoft.Extensions.Options.IOptionsMonitor<Microsoft.Identity.Web.TokenAcquisitionExtensionOptions!>?
 static Microsoft.Identity.Web.TokenAcquisition.ResolveTenant(string? tenant, Microsoft.Identity.Web.MergedOptions! mergedOptions) -> string?
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/PublicAPI.Unshipped.txt
index d1805fb40..68eb4d560 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net472/PublicAPI.Unshipped.txt
@@ -2,6 +2,8 @@
 const Microsoft.Identity.Web.ClaimConstants.Password = "xms_password" -> string!
 const Microsoft.Identity.Web.ClaimConstants.Username = "xms_username" -> string!
 Microsoft.Identity.Web.BeforeTokenAcquisitionForApp
+Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForApp -> Microsoft.Identity.Web.BeforeTokenAcquisitionForApp?
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForTestUser -> Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser?
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.TokenAcquisitionExtensionOptions() -> void
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/InternalAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/InternalAPI.Unshipped.txt
index 74f7de658..d6de268e9 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/InternalAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/InternalAPI.Unshipped.txt
@@ -2,5 +2,6 @@
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.get -> string?
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.set -> void
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForApp(Microsoft.Identity.Client.AcquireTokenForClientParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForTestUser(Microsoft.Identity.Client.AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
 readonly Microsoft.Identity.Web.TokenAcquisition.tokenAcquisitionExtensionOptionsMonitor -> Microsoft.Extensions.Options.IOptionsMonitor<Microsoft.Identity.Web.TokenAcquisitionExtensionOptions!>?
 static Microsoft.Identity.Web.TokenAcquisition.ResolveTenant(string? tenant, Microsoft.Identity.Web.MergedOptions! mergedOptions) -> string?
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/PublicAPI.Unshipped.txt
index d1805fb40..68eb4d560 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net6.0/PublicAPI.Unshipped.txt
@@ -2,6 +2,8 @@
 const Microsoft.Identity.Web.ClaimConstants.Password = "xms_password" -> string!
 const Microsoft.Identity.Web.ClaimConstants.Username = "xms_username" -> string!
 Microsoft.Identity.Web.BeforeTokenAcquisitionForApp
+Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForApp -> Microsoft.Identity.Web.BeforeTokenAcquisitionForApp?
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForTestUser -> Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser?
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.TokenAcquisitionExtensionOptions() -> void
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/InternalAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/InternalAPI.Unshipped.txt
index 74f7de658..d6de268e9 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/InternalAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/InternalAPI.Unshipped.txt
@@ -2,5 +2,6 @@
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.get -> string?
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.set -> void
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForApp(Microsoft.Identity.Client.AcquireTokenForClientParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForTestUser(Microsoft.Identity.Client.AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
 readonly Microsoft.Identity.Web.TokenAcquisition.tokenAcquisitionExtensionOptionsMonitor -> Microsoft.Extensions.Options.IOptionsMonitor<Microsoft.Identity.Web.TokenAcquisitionExtensionOptions!>?
 static Microsoft.Identity.Web.TokenAcquisition.ResolveTenant(string? tenant, Microsoft.Identity.Web.MergedOptions! mergedOptions) -> string?
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/PublicAPI.Unshipped.txt
index d1805fb40..68eb4d560 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net7.0/PublicAPI.Unshipped.txt
@@ -2,6 +2,8 @@
 const Microsoft.Identity.Web.ClaimConstants.Password = "xms_password" -> string!
 const Microsoft.Identity.Web.ClaimConstants.Username = "xms_username" -> string!
 Microsoft.Identity.Web.BeforeTokenAcquisitionForApp
+Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForApp -> Microsoft.Identity.Web.BeforeTokenAcquisitionForApp?
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForTestUser -> Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser?
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.TokenAcquisitionExtensionOptions() -> void
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/InternalAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/InternalAPI.Unshipped.txt
index 74f7de658..d6de268e9 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/InternalAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/InternalAPI.Unshipped.txt
@@ -2,5 +2,6 @@
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.get -> string?
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.set -> void
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForApp(Microsoft.Identity.Client.AcquireTokenForClientParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForTestUser(Microsoft.Identity.Client.AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
 readonly Microsoft.Identity.Web.TokenAcquisition.tokenAcquisitionExtensionOptionsMonitor -> Microsoft.Extensions.Options.IOptionsMonitor<Microsoft.Identity.Web.TokenAcquisitionExtensionOptions!>?
 static Microsoft.Identity.Web.TokenAcquisition.ResolveTenant(string? tenant, Microsoft.Identity.Web.MergedOptions! mergedOptions) -> string?
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/PublicAPI.Unshipped.txt
index d1805fb40..68eb4d560 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/net8.0/PublicAPI.Unshipped.txt
@@ -2,6 +2,8 @@
 const Microsoft.Identity.Web.ClaimConstants.Password = "xms_password" -> string!
 const Microsoft.Identity.Web.ClaimConstants.Username = "xms_username" -> string!
 Microsoft.Identity.Web.BeforeTokenAcquisitionForApp
+Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForApp -> Microsoft.Identity.Web.BeforeTokenAcquisitionForApp?
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForTestUser -> Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser?
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.TokenAcquisitionExtensionOptions() -> void
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/InternalAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/InternalAPI.Unshipped.txt
index 74f7de658..d6de268e9 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/InternalAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/InternalAPI.Unshipped.txt
@@ -2,5 +2,6 @@
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.get -> string?
 Microsoft.Identity.Web.MergedOptions.AppHomeTenantId.set -> void
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForApp(Microsoft.Identity.Client.AcquireTokenForClientParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.InvokeOnBeforeTokenAcquisitionForTestUser(Microsoft.Identity.Client.AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder! builder, Microsoft.Identity.Abstractions.AcquireTokenOptions? acquireTokenOptions) -> void
 readonly Microsoft.Identity.Web.TokenAcquisition.tokenAcquisitionExtensionOptionsMonitor -> Microsoft.Extensions.Options.IOptionsMonitor<Microsoft.Identity.Web.TokenAcquisitionExtensionOptions!>?
 static Microsoft.Identity.Web.TokenAcquisition.ResolveTenant(string? tenant, Microsoft.Identity.Web.MergedOptions! mergedOptions) -> string?
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/PublicAPI.Unshipped.txt
index 5d7a3e9da..dc1044ecc 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/PublicAPI/netstandard2.0/PublicAPI.Unshipped.txt
@@ -1,6 +1,8 @@
 const Microsoft.Identity.Web.ClaimConstants.Password = "xms_password" -> string!
 const Microsoft.Identity.Web.ClaimConstants.Username = "xms_username" -> string!
 Microsoft.Identity.Web.BeforeTokenAcquisitionForApp
+Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForApp -> Microsoft.Identity.Web.BeforeTokenAcquisitionForApp?
+Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.OnBeforeTokenAcquisitionForTestUser -> Microsoft.Identity.Web.BeforeTokenAcquisitionForTestUser?
 Microsoft.Identity.Web.TokenAcquisitionExtensionOptions.TokenAcquisitionExtensionOptions() -> void
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisition.cs b/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisition.cs
index 1c7573616..4d46960cf 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisition.cs
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisition.cs
@@ -357,13 +357,23 @@ public async Task<AuthenticationResult> GetAuthenticationResultForUserAsync(
 
                 }
 
+                // Check for extension options for the ROPC flow
+                TokenAcquisitionExtensionOptions? addInOptions = tokenAcquisitionExtensionOptionsMonitor?.CurrentValue;
+
                 // ROPC flow
-                var authenticationResult = await ((IByUsernameAndPassword)application).AcquireTokenByUsernamePassword(
-                    scopes.Except(_scopesRequestedByMsal),
-                    username,
-                    password)
-                    .ExecuteAsync()
-                    .ConfigureAwait(false);
+                AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder builder = ((IByUsernameAndPassword)application)
+                    .AcquireTokenByUsernamePassword(
+                        scopes.Except(_scopesRequestedByMsal),
+                        username,
+                        password);
+
+                if (addInOptions != null)
+                {
+                    addInOptions.InvokeOnBeforeTokenAcquisitionForTestUser(builder, tokenAcquisitionOptions);
+                }
+
+                var authenticationResult = await builder.ExecuteAsync()
+                .ConfigureAwait(false);
 
                 if (user.GetMsalAccountId() == null)
                 {
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensionOptions.cs b/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensionOptions.cs
index e2a422085..c90dd9f54 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensionOptions.cs
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensionOptions.cs
@@ -28,5 +28,22 @@ internal void InvokeOnBeforeTokenAcquisitionForApp(AcquireTokenForClientParamete
                 OnBeforeTokenAcquisitionForApp(builder, acquireTokenOptions);
             }
         }
+
+        /// <summary>
+        /// Event fired when a ROPC flow request is being built.
+        /// </summary>        
+        public event BeforeTokenAcquisitionForTestUser? OnBeforeTokenAcquisitionForTestUser;
+
+        /// <summary>
+        /// Invoke the BeforeTokenAcquisitionForTestUser event.
+        /// </summary>
+        internal void InvokeOnBeforeTokenAcquisitionForTestUser(AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder builder,
+                                                           AcquireTokenOptions? acquireTokenOptions)
+        {
+            if (OnBeforeTokenAcquisitionForTestUser != null)
+            {
+                OnBeforeTokenAcquisitionForTestUser(builder, acquireTokenOptions);
+            }
+        }
     }
 }
diff --git a/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensions.cs b/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensions.cs
index e4989e54a..9b8fecab8 100644
--- a/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensions.cs
+++ b/src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisitionExtensions.cs
@@ -13,4 +13,11 @@ namespace Microsoft.Identity.Web
     /// <param name="builder">Builder</param>
     /// <param name="acquireTokenOptions">Token acquisition options for the request. Can be null.</param>
     public delegate void BeforeTokenAcquisitionForApp(AcquireTokenForClientParameterBuilder builder, AcquireTokenOptions? acquireTokenOptions);
+
+    /// <summary>
+    /// Signature for token acquisition extensions that act on the request builder, for ROPC flow.
+    /// </summary>
+    /// <param name="builder">Builder</param>
+    /// <param name="acquireTokenOptions">Token acquisition options for the request. Can be null.</param>
+    public delegate void BeforeTokenAcquisitionForTestUser(AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder builder, AcquireTokenOptions? acquireTokenOptions);
 }
diff --git a/src/Microsoft.Identity.Web/PublicAPI/net462/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web/PublicAPI/net462/PublicAPI.Unshipped.txt
index 1fcf3fa79..7dc5c5811 100644
--- a/src/Microsoft.Identity.Web/PublicAPI/net462/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web/PublicAPI/net462/PublicAPI.Unshipped.txt
@@ -1,2 +1 @@
 #nullable enable
-static Microsoft.Identity.Web.ClaimsPrincipalFactory.FromUsernamePassword(string! username, string! password) -> System.Security.Claims.ClaimsPrincipal!
diff --git a/src/Microsoft.Identity.Web/PublicAPI/net472/PublicAPI.Unshipped.txt b/src/Microsoft.Identity.Web/PublicAPI/net472/PublicAPI.Unshipped.txt
index 1fcf3fa79..7dc5c5811 100644
--- a/src/Microsoft.Identity.Web/PublicAPI/net472/PublicAPI.Unshipped.txt
+++ b/src/Microsoft.Identity.Web/PublicAPI/net472/PublicAPI.Unshipped.txt
@@ -1,2 +1 @@
 #nullable enable
-static Microsoft.Identity.Web.ClaimsPrincipalFactory.FromUsernamePassword(string! username, string! password) -> System.Security.Claims.ClaimsPrincipal!
diff --git a/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpCreator.cs b/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpCreator.cs
index 220ef20ab..e3759c223 100644
--- a/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpCreator.cs
+++ b/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpCreator.cs
@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
 
+using System.Collections;
+using System.Collections.Generic;
 using System.Net;
 using System.Net.Http;
 using Microsoft.Identity.Web.Util;
@@ -55,5 +57,17 @@ public static MockHttpMessageHandler CreateClientCredentialTokenHandler(
 
             return handler;
         }
+
+        public static MockHttpMessageHandler CreateHandlerToValidatePostData(
+            HttpMethod expectedMethod,
+            IDictionary<string, string> expectedPostData)
+        {
+            return new MockHttpMessageHandler()
+            {
+                ExpectedMethod = expectedMethod,
+                ExpectedPostData = expectedPostData,
+                ResponseMessage = CreateSuccessfulClientCredentialTokenResponseMessage(),
+            };
+        }
     }
 }
diff --git a/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpMessageHandler.cs b/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpMessageHandler.cs
index 0d609fd1c..488947ae5 100644
--- a/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpMessageHandler.cs
+++ b/tests/Microsoft.Identity.Web.Test.Common/Mocks/MockHttpMessageHandler.cs
@@ -7,6 +7,7 @@
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
+using Azure.Core;
 using Xunit;
 
 namespace Microsoft.Identity.Web.Test.Common.Mocks
@@ -27,6 +28,8 @@ public MockHttpMessageHandler()
 
         public HttpMethod ExpectedMethod { get; set; }
 
+        public IDictionary<string, string> ExpectedPostData { get; set; }
+
         public Exception ExceptionToThrow { get; set; }
 
         /// <summary>
@@ -78,14 +81,28 @@ protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage
             }
 
             Assert.Equal(ExpectedMethod, request.Method);
+            await ValidatePostDataAsync(request);
+            
 
+            return ResponseMessage;
+        }
+
+        private async Task ValidatePostDataAsync(HttpRequestMessage request)
+        {
             if (request.Method != HttpMethod.Get && request.Content != null)
             {
                 string postData = await request.Content.ReadAsStringAsync();
                 ActualRequestPostData = QueryStringParser.ParseKeyValueList(postData, '&', true, false);
             }
 
-            return ResponseMessage;
+            if (ExpectedPostData != null)
+            {
+                foreach (string key in ExpectedPostData.Keys)
+                {
+                    Assert.True(ActualRequestPostData.ContainsKey(key));
+                    Assert.Equal(ExpectedPostData[key], ActualRequestPostData[key]);
+                }
+            }
         }
     }
 }
diff --git a/tests/Microsoft.Identity.Web.Test/TokenAcquisitionAddInTests.cs b/tests/Microsoft.Identity.Web.Test/TokenAcquisitionAddInTests.cs
index 1a33fef50..eb5df222a 100644
--- a/tests/Microsoft.Identity.Web.Test/TokenAcquisitionAddInTests.cs
+++ b/tests/Microsoft.Identity.Web.Test/TokenAcquisitionAddInTests.cs
@@ -7,6 +7,9 @@
 using Microsoft.Identity.Web.Test.Common;
 using Xunit;
 using System.Threading.Tasks;
+using Microsoft.Identity.Client.Extensibility;
+using Microsoft.Graph;
+using System.Collections.Generic;
 
 namespace Microsoft.Identity.Web.Tests
 {
@@ -60,5 +63,55 @@ public async Task InvokeOnBeforeTokenAcquisitionForApp_InvokesEvent()
             Assert.NotNull(result);
             Assert.Equal(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);
         }
+
+        [Fact]
+        public async Task InvokeOnBeforeTokenAcquisitionForUsernamePassword_InvokesEvent()
+        {
+            // Arrange
+            var options = new TokenAcquisitionExtensionOptions();
+            var acquireTokenOptions = new AcquireTokenOptions();
+            acquireTokenOptions.ForceRefresh = true;
+
+            //Configure mocks
+            using MockHttpClientFactory mockHttpClient = new();
+            mockHttpClient.AddMockHandler(MockHttpCreator.CreateHandlerToValidatePostData(
+                System.Net.Http.HttpMethod.Post,
+                new Dictionary<string, string>() { { "x-ms-test", "test" } }));
+
+            var confidentialApp = ConfidentialClientApplicationBuilder
+                           .Create(TestConstants.ClientId)
+                           .WithAuthority(TestConstants.AuthorityCommonTenant)
+                           .WithHttpClientFactory(mockHttpClient)
+                           .WithInstanceDiscovery(false)
+                           .WithClientSecret(TestConstants.ClientSecret)
+                           .Build();
+
+            AcquireTokenByUsernameAndPasswordConfidentialParameterBuilder builder = ((IByUsernameAndPassword)confidentialApp)
+                .AcquireTokenByUsernamePassword(new string[] { "scope" }, "username", "something");
+
+            bool eventInvoked = false;
+            options.OnBeforeTokenAcquisitionForTestUser += (builder, options) =>
+            {
+                MsalAuthenticationExtension extension = new MsalAuthenticationExtension();
+                extension.OnBeforeTokenRequestHandler = (request) =>
+                {
+                    eventInvoked = true;
+                    request.BodyParameters.Add("x-ms-test", "test");
+                    return Task.CompletedTask;
+                };
+
+                builder.WithAuthenticationExtension(extension);
+            };
+
+            // Act
+            options.InvokeOnBeforeTokenAcquisitionForTestUser(builder, acquireTokenOptions);
+
+            var result = await builder.ExecuteAsync();
+
+            // Assert
+            Assert.True(eventInvoked);
+            Assert.NotNull(result);
+            Assert.Equal(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);
+        }
     }
 }