Fixed: Don't process files that don't have a supported media file extension (#2938)

* Fixed: Don't process files that don't have a supported media file extension

(cherry picked from commit 1977f4aa3c55cc0a06e1958e611f366d56cc346e)

* fixup!

* fixup!

Co-authored-by: Mark McDowall <mark@mcdowall.ca>
Co-authored-by: Qstick <qstick@gmail.com>

src/NzbDrone.Core/MediaFiles/DownloadedTracksImportService.cs

@@ -6,6 +6,7 @@ using System.Linq;
 using NLog;
 using NzbDrone.Common.Disk;
 using NzbDrone.Common.EnvironmentInfo;
+using NzbDrone.Common.Extensions;
 using NzbDrone.Core.DecisionEngine;
 using NzbDrone.Core.Download;
 using NzbDrone.Core.MediaFiles.Events;
@@ -276,6 +277,20 @@ namespace NzbDrone.Core.MediaFiles
                        };
             }
 
+            var extension = Path.GetExtension(fileInfo.Name);
+
+            if (extension.IsNullOrWhiteSpace() || !MediaFileExtensions.Extensions.Contains(extension))
+            {
+                _logger.Debug("[{0}] has an unsupported extension: '{1}'", fileInfo.FullName, extension);
+
+                return new List<ImportResult>
+                       {
+                           new ImportResult(new ImportDecision<LocalTrack>(new LocalTrack { Path = fileInfo.FullName },
+                               new Rejection($"Invalid audio file, unsupported extension: '{extension}'")),
+                               $"Invalid audio file, unsupported extension: '{extension}'")
+                       };
+            }
+
             if (downloadClientItem == null)
             {
                 if (_diskProvider.IsFileLocked(fileInfo.FullName))