diff --git a/MediaBrowser.Controller/Entities/BaseItem.cs b/MediaBrowser.Controller/Entities/BaseItem.cs
index 8f89c1c797..e312e9d80b 100644
--- a/MediaBrowser.Controller/Entities/BaseItem.cs
+++ b/MediaBrowser.Controller/Entities/BaseItem.cs
@@ -1171,11 +1171,18 @@ namespace MediaBrowser.Controller.Entities
                 info.Video3DFormat = video.Video3DFormat;
                 info.Timestamp = video.Timestamp;
 
-                if (video.IsShortcut)
+                if (video.IsShortcut && !string.IsNullOrEmpty(video.ShortcutPath))
                 {
-                    info.IsRemote = true;
-                    info.Path = video.ShortcutPath;
-                    info.Protocol = MediaSourceManager.GetPathProtocol(info.Path);
+                    var shortcutProtocol = MediaSourceManager.GetPathProtocol(video.ShortcutPath);
+
+                    // Only allow remote shortcut paths — local file paths in .strm files
+                    // could be used to read arbitrary files from the server.
+                    if (shortcutProtocol != MediaProtocol.File)
+                    {
+                        info.IsRemote = true;
+                        info.Path = video.ShortcutPath;
+                        info.Protocol = shortcutProtocol;
+                    }
                 }
 
                 if (string.IsNullOrEmpty(info.Container))
diff --git a/MediaBrowser.Providers/MediaInfo/ProbeProvider.cs b/MediaBrowser.Providers/MediaInfo/ProbeProvider.cs
index 9f5463b82c..c3ff26202f 100644
--- a/MediaBrowser.Providers/MediaInfo/ProbeProvider.cs
+++ b/MediaBrowser.Providers/MediaInfo/ProbeProvider.cs
@@ -262,9 +262,28 @@ namespace MediaBrowser.Providers.MediaInfo
 
         private void FetchShortcutInfo(BaseItem item)
         {
-            item.ShortcutPath = File.ReadAllLines(item.Path)
+            var shortcutPath = File.ReadAllLines(item.Path)
                 .Select(NormalizeStrmLine)
                 .FirstOrDefault(i => !string.IsNullOrWhiteSpace(i) && !i.StartsWith('#'));
+
+            if (string.IsNullOrWhiteSpace(shortcutPath))
+            {
+                return;
+            }
+
+            // Only allow remote URLs in .strm files to prevent local file access
+            if (Uri.TryCreate(shortcutPath, UriKind.Absolute, out var uri)
+                && (string.Equals(uri.Scheme, "http", StringComparison.OrdinalIgnoreCase)
+                    || string.Equals(uri.Scheme, "https", StringComparison.OrdinalIgnoreCase)
+                    || string.Equals(uri.Scheme, "rtsp", StringComparison.OrdinalIgnoreCase)
+                    || string.Equals(uri.Scheme, "rtp", StringComparison.OrdinalIgnoreCase)))
+            {
+                item.ShortcutPath = shortcutPath;
+            }
+            else
+            {
+                _logger.LogWarning("Ignoring invalid or non-remote .strm path in {File}: {Path}", item.Path, shortcutPath);
+            }
         }
 
         /// <summary>
diff --git a/MediaBrowser.Providers/Subtitles/SubtitleManager.cs b/MediaBrowser.Providers/Subtitles/SubtitleManager.cs
index 420dd39a48..9f95a9d959 100644
--- a/MediaBrowser.Providers/Subtitles/SubtitleManager.cs
+++ b/MediaBrowser.Providers/Subtitles/SubtitleManager.cs
@@ -7,6 +7,7 @@ using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using Emby.Naming.Common;
 using Jellyfin.Extensions;
 using MediaBrowser.Common.Extensions;
 using MediaBrowser.Controller.Entities;
@@ -32,6 +33,7 @@ namespace MediaBrowser.Providers.Subtitles
         private readonly ILibraryMonitor _monitor;
         private readonly IMediaSourceManager _mediaSourceManager;
         private readonly ILocalizationManager _localization;
+        private readonly HashSet<string> _allowedSubtitleFormats;
 
         private readonly ISubtitleProvider[] _subtitleProviders;
 
@@ -41,7 +43,8 @@ namespace MediaBrowser.Providers.Subtitles
             ILibraryMonitor monitor,
             IMediaSourceManager mediaSourceManager,
             ILocalizationManager localizationManager,
-            IEnumerable<ISubtitleProvider> subtitleProviders)
+            IEnumerable<ISubtitleProvider> subtitleProviders,
+            NamingOptions namingOptions)
         {
             _logger = logger;
             _fileSystem = fileSystem;
@@ -51,6 +54,9 @@ namespace MediaBrowser.Providers.Subtitles
             _subtitleProviders = subtitleProviders
                 .OrderBy(i => i is IHasOrder hasOrder ? hasOrder.Order : 0)
                 .ToArray();
+            _allowedSubtitleFormats = new HashSet<string>(
+                namingOptions.SubtitleFileExtensions.Select(e => e.TrimStart('.')),
+                StringComparer.OrdinalIgnoreCase);
         }
 
         /// <inheritdoc />
@@ -171,6 +177,12 @@ namespace MediaBrowser.Providers.Subtitles
         /// <inheritdoc />
         public Task UploadSubtitle(Video video, SubtitleResponse response)
         {
+            var format = response.Format;
+            if (string.IsNullOrEmpty(format) || !_allowedSubtitleFormats.Contains(format))
+            {
+                throw new ArgumentException($"Unsupported subtitle format: '{format}'");
+            }
+
             var libraryOptions = BaseItem.LibraryManager.GetLibraryOptions(video);
             return TrySaveSubtitle(video, libraryOptions, response);
         }
@@ -230,7 +242,7 @@ namespace MediaBrowser.Providers.Subtitles
 
             foreach (var savePath in savePaths)
             {
-                var path = savePath + "." + extension;
+                var path = Path.GetFullPath(savePath + "." + extension);
                 try
                 {
                     if (path.StartsWith(video.ContainingFolderPath, StringComparison.Ordinal)
@@ -241,7 +253,7 @@ namespace MediaBrowser.Providers.Subtitles
 
                         while (fileExists)
                         {
-                            path = string.Format(CultureInfo.InvariantCulture, "{0}.{1}.{2}", savePath, counter, extension);
+                            path = Path.GetFullPath(string.Format(CultureInfo.InvariantCulture, "{0}.{1}.{2}", savePath, counter, extension));
                             fileExists = File.Exists(path);
                             counter++;
                         }