Clears the auth cookie after install if there is one which forces the login screen to display so that the csrf tokens are created - this is required if you are upgrading from a previous version and are logged in but don't have a version with csrf tokens.

src/Umbraco.Web.UI/install/steps/TheEnd.ascx.cs

@@ -1,5 +1,9 @@
 using System;
+using System.Web;
+using Umbraco.Core;
 using Umbraco.Core.Configuration;
+using Umbraco.Core.Logging;
+using Umbraco.Web.Security;
 
 namespace Umbraco.Web.UI.Install.Steps
 {
@@ -12,15 +16,20 @@ namespace Umbraco.Web.UI.Install.Steps
             {
                 GlobalSettings.ConfigurationStatus = UmbracoVersion.Current.ToString(3);
             }
-            catch (Exception)
+            catch (Exception ex)
             {
-                //errorLiteral.Text = ex.ToString();
+                LogHelper.Error<TheEnd>("An error occurred updating the config status", ex);
             }
 
             // Update ClientDependency version
             var clientDependencyConfig = new ClientDependencyConfiguration();
             var clientDependencyUpdated = clientDependencyConfig.IncreaseVersionNumber();
             
+            //Clear the auth cookie - this is required so that the login screen is displayed after upgrade and so the 
+            // csrf anti-forgery tokens are created, otherwise there will just be JS errors if the user has an old 
+            // login token from a previous version when we didn't have csrf tokens in place
+            var security = new WebSecurity(new HttpContextWrapper(Context), ApplicationContext.Current);
+            security.ClearCurrentLogin();
         }
 
     }