diff --git a/src/Microsoft.Identity.Abstractions/TokenAcquisition/AcquireTokenOptions.cs b/src/Microsoft.Identity.Abstractions/TokenAcquisition/AcquireTokenOptions.cs
index 81d2539..1c7a896 100644
--- a/src/Microsoft.Identity.Abstractions/TokenAcquisition/AcquireTokenOptions.cs
+++ b/src/Microsoft.Identity.Abstractions/TokenAcquisition/AcquireTokenOptions.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 
 namespace Microsoft.Identity.Abstractions
 {
@@ -30,6 +31,7 @@ public AcquireTokenOptions(AcquireTokenOptions other)
             CorrelationId = other.CorrelationId;
             ExtraQueryParameters = other.ExtraQueryParameters;
             ExtraHeadersParameters = other.ExtraHeadersParameters;
+            ExtraParameters = other.ExtraParameters;
             ForceRefresh = other.ForceRefresh;
             Claims = other.Claims;
             PopPublicKey = other.PopPublicKey;
@@ -58,6 +60,15 @@ public AcquireTokenOptions(AcquireTokenOptions other)
         /// </summary>
         public IDictionary<string, string>? ExtraQueryParameters { get; set; }
 
+        /// <summary>
+        /// An property bag used for extensiblity. 
+        /// </summary>
+        /// <remarks>
+        /// Not meant to be used by application developers, but by other SDKs.
+        /// </remarks>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public IDictionary<string, object>? ExtraParameters { get; set; }
+
         /// Sets extra headers in the HTTP request to the STS "/token" endpoint.
         public IDictionary<string, string>? ExtraHeadersParameters { get; set; }
 
diff --git a/test/Microsoft.Identity.Abstractions.Tests/DownstreamApiTests.cs b/test/Microsoft.Identity.Abstractions.Tests/DownstreamApiTests.cs
index b7445b0..4edfae4 100644
--- a/test/Microsoft.Identity.Abstractions.Tests/DownstreamApiTests.cs
+++ b/test/Microsoft.Identity.Abstractions.Tests/DownstreamApiTests.cs
@@ -32,6 +32,7 @@ public void CloneClonesAllProperties()
                     CorrelationId = Guid.NewGuid(),
                     ExtraHeadersParameters = new Dictionary<string, string> { { "slice", "test" } },
                     ExtraQueryParameters = new Dictionary<string, string> { { "slice", "test" } },
+                    ExtraParameters = new Dictionary<string, object> { { "param1", "value1" }, { "param2", "value2" } },
                     ForceRefresh = true,
                     LongRunningWebApiSessionKey = AcquireTokenOptions.LongRunningWebApiSessionKeyAuto,
                     ManagedIdentity = new ManagedIdentityOptions(),
@@ -81,6 +82,7 @@ public void CloneClonesAllProperties()
             Assert.Equal(downstreamApiOptions.AcquireTokenOptions.CorrelationId, downstreamApiClone.AcquireTokenOptions.CorrelationId);
             Assert.Equal(downstreamApiOptions.AcquireTokenOptions.ExtraHeadersParameters, downstreamApiClone.AcquireTokenOptions.ExtraHeadersParameters);
             Assert.Equal(downstreamApiOptions.AcquireTokenOptions.ExtraQueryParameters, downstreamApiClone.AcquireTokenOptions.ExtraQueryParameters);
+            Assert.Equal(downstreamApiOptions.AcquireTokenOptions.ExtraParameters, downstreamApiClone.AcquireTokenOptions.ExtraParameters);
             Assert.Equal(downstreamApiOptions.AcquireTokenOptions.ForceRefresh, downstreamApiClone.AcquireTokenOptions.ForceRefresh);
             Assert.Equal(downstreamApiOptions.AcquireTokenOptions.LongRunningWebApiSessionKey, downstreamApiClone.AcquireTokenOptions.LongRunningWebApiSessionKey);
             Assert.Equal(downstreamApiOptions.AcquireTokenOptions.ManagedIdentity.UserAssignedClientId, downstreamApiClone.AcquireTokenOptions.ManagedIdentity?.UserAssignedClientId);
@@ -93,7 +95,7 @@ public void CloneClonesAllProperties()
 
             // If this fails, think of also adding a line to test the new property
             Assert.Equal(12, typeof(DownstreamApiOptions).GetProperties().Length);
-            Assert.Equal(13, typeof(AcquireTokenOptions).GetProperties().Length);
+            Assert.Equal(14, typeof(AcquireTokenOptions).GetProperties().Length);
 
             DownstreamApiOptionsReadOnlyHttpMethod options = new DownstreamApiOptionsReadOnlyHttpMethod(downstreamApiOptions, HttpMethod.Delete.ToString());
             Assert.Equal(HttpMethod.Delete.ToString(), options.HttpMethod);