diff --git a/src/Umbraco.Core/Configuration/ContentSettingsExtensions.cs b/src/Umbraco.Core/Configuration/ContentSettingsExtensions.cs
index 9c1f5faef9..94e2968056 100644
--- a/src/Umbraco.Core/Configuration/ContentSettingsExtensions.cs
+++ b/src/Umbraco.Core/Configuration/ContentSettingsExtensions.cs
@@ -14,8 +14,8 @@ public static class ContentSettingsExtensions
     ///   <c>true</c> if the file extension is allowed for upload; otherwise, <c>false</c>.
     /// </returns>
     public static bool IsFileAllowedForUpload(this ContentSettings contentSettings, string extension)
-        => contentSettings.AllowedUploadedFileExtensions.Any(x => x.InvariantEquals(extension)) ||
-        (contentSettings.AllowedUploadedFileExtensions.Any() == false && contentSettings.DisallowedUploadedFileExtensions.Any(x => x.InvariantEquals(extension)) == false);
+        => contentSettings.AllowedUploadedFileExtensions.Any(x => x.InvariantEquals(extension.Trim())) ||
+        (contentSettings.AllowedUploadedFileExtensions.Any() == false && contentSettings.DisallowedUploadedFileExtensions.Any(x => x.InvariantEquals(extension.Trim())) == false);
 
     /// <summary>
     /// Gets the auto-fill configuration for a specified property alias.
diff --git a/tests/Umbraco.Tests.UnitTests/Umbraco.Core/Configuration/ContentSettingsExtensionsTests.cs b/tests/Umbraco.Tests.UnitTests/Umbraco.Core/Configuration/ContentSettingsExtensionsTests.cs
new file mode 100644
index 0000000000..3558a0bd5b
--- /dev/null
+++ b/tests/Umbraco.Tests.UnitTests/Umbraco.Core/Configuration/ContentSettingsExtensionsTests.cs
@@ -0,0 +1,76 @@
+// Copyright (c) Umbraco.
+// See LICENSE for more details.
+
+using NUnit.Framework;
+using Umbraco.Cms.Core.Configuration.Models;
+using Umbraco.Extensions;
+
+namespace Umbraco.Cms.Tests.UnitTests.Umbraco.Core.Configuration;
+
+[TestFixture]
+public class ContentSettingsExtensionsTests
+{
+    [TestCase("jpg")]
+    [TestCase("JPG")]
+    [TestCase("jpg ")]
+    public void IsFileAllowedForUpload_Allows_File_In_Allow_List(string extension)
+    {
+        var contentSettings = new ContentSettings
+        {
+            AllowedUploadedFileExtensions = new[] { "jpg", "png" }.ToHashSet(),
+        };
+
+        Assert.IsTrue(contentSettings.IsFileAllowedForUpload(extension));
+    }
+
+    [TestCase("gif")]
+    [TestCase("GIF")]
+    [TestCase("gif ")]
+    public void IsFileAllowedForUpload_Rejects_File_Not_In_Allow_List(string extension)
+    {
+        var contentSettings = new ContentSettings
+        {
+            AllowedUploadedFileExtensions = new[] { "jpg", "png" }.ToHashSet(),
+        };
+
+        Assert.IsFalse(contentSettings.IsFileAllowedForUpload(extension));
+    }
+
+    [TestCase("jpg")]
+    [TestCase("JPG")]
+    [TestCase("jpg ")]
+    public void IsFileAllowedForUpload_Allows_File_Not_In_Disallow_List(string extension)
+    {
+        var contentSettings = new ContentSettings
+        {
+            DisallowedUploadedFileExtensions = new[] { "gif", "png" }.ToHashSet(),
+        };
+
+        Assert.IsTrue(contentSettings.IsFileAllowedForUpload(extension));
+    }
+
+    [TestCase("gif")]
+    [TestCase("GIF")]
+    [TestCase("gif ")]
+    public void IsFileAllowedForUpload_Rejects_File_In_Disallow_List(string extension)
+    {
+        var contentSettings = new ContentSettings
+        {
+            DisallowedUploadedFileExtensions = new[] { "gif", "png" }.ToHashSet(),
+        };
+
+        Assert.IsFalse(contentSettings.IsFileAllowedForUpload(extension));
+    }
+
+    [Test]
+    public void IsFileAllowedForUpload_Allows_File_In_Allow_List_Even_If_Also_In_Disallow_List()
+    {
+        var contentSettings = new ContentSettings
+        {
+            AllowedUploadedFileExtensions = new[] { "jpg", "png" }.ToHashSet(),
+            DisallowedUploadedFileExtensions = new[] { "jpg", }.ToHashSet(),
+        };
+
+        Assert.IsTrue(contentSettings.IsFileAllowedForUpload("jpg"));
+    }
+}