diff --git a/DNN Platform/Library/Services/GeneratedImage/DnnImageHandler.cs b/DNN Platform/Library/Services/GeneratedImage/DnnImageHandler.cs
index d8562ac1cca..8ed6be13c47 100644
--- a/DNN Platform/Library/Services/GeneratedImage/DnnImageHandler.cs	
+++ b/DNN Platform/Library/Services/GeneratedImage/DnnImageHandler.cs	
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Configuration;
 using System.Drawing;
@@ -233,11 +234,14 @@ public override ImageInfo GenerateImage(NameValueCollection parameters)
                         }
                         else if (!string.IsNullOrEmpty(parameters["Url"]))
                         {
-                            if (!parameters["Url"].StartsWith("http"))
+                            var url = parameters["Url"];
+                            // allow only site resources when using the url parameter
+                            if (!url.StartsWith("http") || !UriBelongsToSite(new Uri(url)))
                             {
                                 return GetEmptyImageInfo();
                             }
-                            imgUrl = parameters["Url"];
+
+                            imgUrl = url;
                         }
 
                         if (string.IsNullOrEmpty(parameters["format"]))
@@ -555,5 +559,20 @@ private static ImageFormat GetImageFormat(string extension)
                     return ImageFormat.Png;
             }
         }
+
+        // checks whether the uri belongs to any of the site-wide aliases
+        private static bool UriBelongsToSite(Uri uri)
+        {
+            IEnumerable<string> hostAliases =
+                from PortalAliasInfo alias in PortalAliasController.Instance.GetPortalAliases().Values
+                 select alias.HTTPAlias.ToLowerInvariant();
+
+            // if URI, for example, = "http(s)://myDomain:80/DNNDev/myPage?var=name" , then the two strings will be
+            // uriNoScheme1 = "mydomain/dnndev/mypage"  -- lower case
+            // uriNoScheme2 = "mydomain:80/dnndev/mypage"  -- lower case
+            var uriNoScheme1 = (uri.DnsSafeHost + uri.LocalPath).ToLowerInvariant();
+            var uriNoScheme2 = (uri.Authority + uri.LocalPath).ToLowerInvariant();
+            return hostAliases.Any(alias => uriNoScheme1.StartsWith(alias) || uriNoScheme2.StartsWith(alias));
+        }
     }
 }
\ No newline at end of file
diff --git a/DNN Platform/Library/Services/GeneratedImage/FilterTransform/ImageResizeTransform.cs b/DNN Platform/Library/Services/GeneratedImage/FilterTransform/ImageResizeTransform.cs
index ad8a3b67e84..786b072c54b 100644
--- a/DNN Platform/Library/Services/GeneratedImage/FilterTransform/ImageResizeTransform.cs	
+++ b/DNN Platform/Library/Services/GeneratedImage/FilterTransform/ImageResizeTransform.cs	
@@ -113,7 +113,10 @@ public ImageResizeTransform() {
         /// <param name="image">Input image</param>
         /// <returns>Image result after image transformation</returns>
         public override Image ProcessImage(Image image)
-		{
+        {
+            if (image == null)
+                return null;    
+
             if (MaxWidth > 0)
             {
                 Width = image.Width > MaxWidth ? MaxWidth : image.Width;
diff --git a/DNN Platform/Library/Services/GeneratedImage/ImageHandlerInternal.cs b/DNN Platform/Library/Services/GeneratedImage/ImageHandlerInternal.cs
index a5a0f2ae24f..94528aae71b 100644
--- a/DNN Platform/Library/Services/GeneratedImage/ImageHandlerInternal.cs	
+++ b/DNN Platform/Library/Services/GeneratedImage/ImageHandlerInternal.cs	
@@ -426,7 +426,7 @@ private void RenderImage(Image image, Stream outStream)
                         Param = { [0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, ImageCompression) }
                     };
                     var ici = GetEncoderInfo(GetImageMimeType(ContentType));
-                    image.Save(outStream, ici, eps);
+                    image?.Save(outStream, ici, eps);
                 }
             }
             finally
diff --git a/DNN Platform/Tests/DNN.Integration.Test.Framework/DNN.Integration.Test.Framework.csproj b/DNN Platform/Tests/DNN.Integration.Test.Framework/DNN.Integration.Test.Framework.csproj
index 2499a53400c..b159844446c 100644
--- a/DNN Platform/Tests/DNN.Integration.Test.Framework/DNN.Integration.Test.Framework.csproj	
+++ b/DNN Platform/Tests/DNN.Integration.Test.Framework/DNN.Integration.Test.Framework.csproj	
@@ -81,6 +81,7 @@
     <Compile Include="Helpers\FolderHelper.cs" />
     <Compile Include="Helpers\HostSettingsHelper.cs" />
     <Compile Include="Helpers\MockComponentHelper.cs" />
+    <Compile Include="Helpers\PortalAliasHelper.cs" />
     <Compile Include="Helpers\PortalInfoHelper.cs" />
     <Compile Include="Helpers\PortalSettingsHelper.cs" />
     <Compile Include="Helpers\StoredProcedureStatsHelper.cs" />
diff --git a/DNN Platform/Tests/DNN.Integration.Test.Framework/Helpers/PortalAliasHelper.cs b/DNN Platform/Tests/DNN.Integration.Test.Framework/Helpers/PortalAliasHelper.cs
new file mode 100644
index 00000000000..615da9c1b25
--- /dev/null
+++ b/DNN Platform/Tests/DNN.Integration.Test.Framework/Helpers/PortalAliasHelper.cs	
@@ -0,0 +1,40 @@
+// DotNetNuke® - http://www.dnnsoftware.com
+// Copyright (c) 2002-2018, DNN Corp.
+// All Rights Reserved
+
+using System.Collections.Generic;
+using System.Linq;
+using DotNetNuke.Entities.Portals;
+
+namespace DNN.Integration.Test.Framework.Helpers
+{
+    public class PortalAliasHelper
+    {
+        public static PortalAliasInfo GetPrimaryPortalAlias(int portalId = 0)
+        {
+            return DatabaseHelper.ExecuteStoredProcedure<PortalAliasInfo>("GetPortalAliases").First(p => p.PortalID == portalId && p.IsPrimary);
+        }
+
+        public static IEnumerable<PortalAliasInfo> GetPortalAliaes(int portalId = 0)
+        {
+            return DatabaseHelper.ExecuteStoredProcedure<PortalAliasInfo>("GetPortalAliases").Where(p => p.PortalID == portalId);
+        }
+
+        public static IEnumerable<PortalAliasInfo> GetAllPortalAliaes()
+        {
+            return DatabaseHelper.ExecuteStoredProcedure<PortalAliasInfo>("GetPortalAliases");
+        }
+
+        public static void AddPortalAlias(PortalAliasInfo portal)
+        {
+            DatabaseHelper.ExecuteStoredProcedure("AddPortalAlias",
+                portal.PortalID,
+                portal.HTTPAlias,
+                portal.CultureCode,
+                portal.Skin,
+                portal.BrowserType,
+                portal.IsPrimary,
+                -1);
+        }
+    }
+}
diff --git a/DNN Platform/Tests/DotNetNuke.Tests.Integration/DotNetNuke.Tests.Integration.csproj b/DNN Platform/Tests/DotNetNuke.Tests.Integration/DotNetNuke.Tests.Integration.csproj
index b47625bbb59..7e7274f3894 100644
--- a/DNN Platform/Tests/DotNetNuke.Tests.Integration/DotNetNuke.Tests.Integration.csproj	
+++ b/DNN Platform/Tests/DotNetNuke.Tests.Integration/DotNetNuke.Tests.Integration.csproj	
@@ -98,6 +98,7 @@
     <Compile Include="PersonaBar\Content\Pages\AddPageTests.cs" />
     <Compile Include="PersonaBar\Content\Pages\PageUrlsTests.cs" />
     <Compile Include="PersonaBar\Manage\Users\UsersFiltersTests.cs" />
+    <Compile Include="Tests\Library\ImageHandlerTests.cs" />
     <Compile Include="Tests\Portals\PortalInfoTests.cs" />
     <Compile Include="Tests\Portals\PortalSettingsTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
diff --git a/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Library/ImageHandlerTests.cs b/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Library/ImageHandlerTests.cs
new file mode 100644
index 00000000000..32bc2811ad1
--- /dev/null
+++ b/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Library/ImageHandlerTests.cs	
@@ -0,0 +1,76 @@
+// DotNetNuke® - http://www.dnnsoftware.com
+// Copyright (c) 2002-2018, DNN Corp.
+// All Rights Reserved
+
+using System.Linq;
+using DNN.Integration.Test.Framework;
+using DNN.Integration.Test.Framework.Helpers;
+using DotNetNuke.Entities.Portals;
+using NUnit.Framework;
+
+namespace DotNetNuke.Tests.Integration.Tests.Library
+{
+    [TestFixture]
+    public class ImageHandlerTests : IntegrationTestBase
+    {
+        // we assume this GIF image exists in all DNN sites and it shouldn't be PNG
+        private const string HandlerPath = "/DnnImageHandler.ashx?mode=file&w=1&url={0}/images/1x1.GIF";
+
+        [Test]
+        public void Using_Image_Handler_For_Foreign_Site_ShouldFail()
+        {
+            var session = WebApiTestHelper.GetAnnonymousConnector();
+            var relativeUrl = string.Format(HandlerPath, "https://google.com");
+
+            var response = session.GetContent(relativeUrl).Content.ReadAsStringAsync().Result;
+            Assert.IsTrue(response.StartsWith("�PNG\r\n"), $"Content = {response}");
+        }
+
+        [Test]
+        public void Using_Image_Handler_For_Main_Alias_ShouldPass()
+        {
+            var session = WebApiTestHelper.GetAnnonymousConnector();
+            var relativeUrl = string.Format(HandlerPath, AppConfigHelper.SiteUrl);
+
+            var response = session.GetContent(relativeUrl).Content.ReadAsStringAsync().Result;
+            Assert.IsTrue(response.StartsWith("GIF89a"), $"Content = {response}");
+        }
+
+        [Test]
+        public void Using_Image_Handler_From_All_Alias_ShouldPass()
+        {
+            PortalAliasInfo pai;
+            var aliases = PortalAliasHelper.GetPortalAliaes().ToList();
+            if (aliases.Count == 1)
+            {
+                var primary = aliases.First();
+                pai = new PortalAliasInfo
+                {
+                    PortalID = primary.PortalID,
+                    HTTPAlias = "my-" + primary.HTTPAlias,
+                    CultureCode = primary.CultureCode,
+                    Skin = primary.Skin,
+                    BrowserType = primary.BrowserType,
+                    IsPrimary = false,
+
+                };
+            }
+            else
+            {
+                pai = aliases.First(a => a.PortalAliasID > 1);
+            }
+
+            var session = WebApiTestHelper.GetAnnonymousConnector();
+            aliases = PortalAliasHelper.GetPortalAliaes().ToList();
+            foreach (var alias in aliases)
+            {
+                var relativeUrl = string.Format(HandlerPath, AppConfigHelper.SiteUrl);
+                var absoluteUrl = $"http://{alias.HTTPAlias}{relativeUrl}";
+                LogText("Getting image from " + absoluteUrl);
+
+                var response = session.GetContent(absoluteUrl).Content.ReadAsStringAsync().Result;
+                Assert.IsTrue(response.StartsWith("GIF89a"), $"Url: {absoluteUrl} / Content = {response}");
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Security/AuthCookieTests.cs b/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Security/AuthCookieTests.cs
index 720d39116ef..223159ece97 100644
--- a/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Security/AuthCookieTests.cs	
+++ b/DNN Platform/Tests/DotNetNuke.Tests.Integration/Tests/Security/AuthCookieTests.cs	
@@ -1,8 +1,10 @@
-using System;
+// DotNetNuke® - http://www.dnnsoftware.com
+// Copyright (c) 2002-2018, DNN Corp.
+// All Rights Reserved
+
+using System;
 using System.Net;
 using System.Net.Http;
-using System.Net.Http.Headers;
-using System.Threading;
 using DNN.Integration.Test.Framework;
 using DNN.Integration.Test.Framework.Helpers;
 using NUnit.Framework;