Fix for exception throw when validating URLs (#7701)

src/Umbraco.Core/StringExtensions.cs

@@ -79,6 +79,21 @@ namespace Umbraco.Core
 
         }
 
+        /// <summary>
+        /// Determines the extension of the path or URL
+        /// </summary>
+        /// <param name="file"></param>
+        /// <returns>Extension of the file</returns>
+        public static string GetFileExtension(this string file)
+        {
+            //Find any characters between the last . and the start of a query string or the end of the string
+            const string pattern = @"(?<extension>\.[^\.\?]+)(\?.*|$)";
+            var match = Regex.Match(file, pattern);
+            return match.Success
+                ? match.Groups["extension"].Value
+                : string.Empty;
+        }
+
         /// <summary>
         /// Based on the input string, this will detect if the string is a JS path or a JS snippet.
         /// If a path cannot be determined, then it is assumed to be a snippet the original text is returned

src/Umbraco.Tests/Strings/StringExtensionsTests.cs

@@ -70,6 +70,24 @@ namespace Umbraco.Tests.Strings
             Assert.AreEqual(stripped, result);
         }
 
+        [TestCase("../wtf.js?x=wtf", ".js")]
+        [TestCase(".htaccess", ".htaccess")]
+        [TestCase("path/to/file/image.png", ".png")]
+        [TestCase("c:\\abc\\def\\ghi.jkl", ".jkl")]
+        [TestCase("/root/folder.name/file.ext", ".ext")]
+        [TestCase("http://www.domain.com/folder/name/file.txt", ".txt")]
+        [TestCase("i/don't\\have\\an/extension", "")]
+        [TestCase("https://some.where/path/to/file.ext?query=this&more=that", ".ext")]
+        [TestCase("double_query.string/file.ext?query=abc?something.else", ".ext")]
+        [TestCase("test.tar.gz", ".gz")]
+        [TestCase("wierd.file,but._legal", "._legal")]
+        [TestCase("one_char.x", ".x")]
+        public void Get_File_Extension(string input, string result)
+        {
+            var extension = input.GetFileExtension();
+            Assert.AreEqual(result, extension);
+        }
+
         [TestCase("'+alert(1234)+'", "+alert1234+")]
         [TestCase("'+alert(56+78)+'", "+alert56+78+")]
         [TestCase("{{file}}", "file")]

src/Umbraco.Web/PropertyEditors/UploadFileTypeValidator.cs

@@ -48,7 +48,7 @@ namespace Umbraco.Web.PropertyEditors
         internal static bool IsValidFileExtension(string fileName)
         {
             if (fileName.IndexOf('.') <= 0) return false;
-            var extension = new FileInfo(fileName).Extension.TrimStart(".");
+            var extension = fileName.GetFileExtension().TrimStart(".");
             return Current.Configs.Settings().Content.IsFileAllowedForUpload(extension);
         }
     }