From e0eadf2cf5f4548443c60da43df3f0416e470cdb Mon Sep 17 00:00:00 2001
From: Kenn Jacobsen <kja@vertica.dk>
Date: Mon, 12 Oct 2020 17:10:22 +0200
Subject: [PATCH] Creating a "System" content type breaks Umbraco (#9005)

---
 .../BackOffice/ContentTypeModelValidatorBase.cs        | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/Umbraco.ModelsBuilder.Embedded/BackOffice/ContentTypeModelValidatorBase.cs b/src/Umbraco.ModelsBuilder.Embedded/BackOffice/ContentTypeModelValidatorBase.cs
index 15ca2cca24..4051bc3bd5 100644
--- a/src/Umbraco.ModelsBuilder.Embedded/BackOffice/ContentTypeModelValidatorBase.cs
+++ b/src/Umbraco.ModelsBuilder.Embedded/BackOffice/ContentTypeModelValidatorBase.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.Linq;
 using Umbraco.Core;
@@ -25,6 +26,13 @@ namespace Umbraco.ModelsBuilder.Embedded.BackOffice
             //don't do anything if we're not enabled
             if (!_config.Enable) yield break;
 
+            //list of reserved/disallowed aliases for content/media/member types - more can be added as the need arises
+            var reservedModelAliases = new[] { "system" };
+            if(reservedModelAliases.Contains(model.Alias, StringComparer.OrdinalIgnoreCase))
+            {
+                yield return new ValidationResult($"The model alias {model.Alias} is a reserved term and cannot be used", new[] { "Alias" });
+            }
+
             var properties = model.Groups.SelectMany(x => x.Properties)
                 .Where(x => x.Inherited == false)
                 .ToArray();