diff --git a/MediaBrowser.Controller/ClientEvent/ClientEventLogger.cs b/MediaBrowser.Controller/ClientEvent/ClientEventLogger.cs
index 14dc64dabd..36f0d2195c 100644
--- a/MediaBrowser.Controller/ClientEvent/ClientEventLogger.cs
+++ b/MediaBrowser.Controller/ClientEvent/ClientEventLogger.cs
@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Threading.Tasks;
+using Jellyfin.Extensions;
 
 namespace MediaBrowser.Controller.ClientEvent
 {
@@ -21,8 +22,15 @@ namespace MediaBrowser.Controller.ClientEvent
         /// <inheritdoc />
         public async Task<string> WriteDocumentAsync(string clientName, string clientVersion, Stream fileContents)
         {
-            var fileName = $"upload_{clientName}_{clientVersion}_{DateTime.UtcNow:yyyyMMddHHmmss}_{Guid.NewGuid():N}.log";
+            var safeClientName = PathHelper.GetSafeLeafFileName(clientName) ?? "unknown-client";
+            var safeClientVersion = PathHelper.GetSafeLeafFileName(clientVersion) ?? "unknown-version";
+            var fileName = $"upload_{safeClientName}_{safeClientVersion}_{DateTime.UtcNow:yyyyMMddHHmmss}_{Guid.NewGuid():N}.log";
             var logFilePath = Path.Combine(_applicationPaths.LogDirectoryPath, fileName);
+            if (!PathHelper.IsContainedIn(_applicationPaths.LogDirectoryPath, logFilePath))
+            {
+                throw new ArgumentException("Path resolved to filename not in log directory");
+            }
+
             var fileStream = new FileStream(logFilePath, FileMode.CreateNew, FileAccess.Write, FileShare.None);
             await using (fileStream.ConfigureAwait(false))
             {
diff --git a/tests/Jellyfin.Controller.Tests/ClientEventLoggerTests.cs b/tests/Jellyfin.Controller.Tests/ClientEventLoggerTests.cs
new file mode 100644
index 0000000000..5132e529dd
--- /dev/null
+++ b/tests/Jellyfin.Controller.Tests/ClientEventLoggerTests.cs
@@ -0,0 +1,44 @@
+using System;
+using System.IO;
+using System.Text;
+using System.Threading.Tasks;
+using MediaBrowser.Controller;
+using MediaBrowser.Controller.ClientEvent;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Controller.Tests
+{
+    public class ClientEventLoggerTests
+    {
+        [Theory]
+        [InlineData("../../../../etc/passwd", "1.0")]
+        [InlineData("..\\..\\windows\\system32", "1.0")]
+        [InlineData("normal-client", "../../../etc/passwd")]
+        [InlineData("/absolute/path", "1.0")]
+        public async Task WriteDocumentAsync_TraversalInput_StaysInsideLogDirectory(string clientName, string clientVersion)
+        {
+            var logDir = Path.Combine(Path.GetTempPath(), "jellyfin-clientlog-test-" + Path.GetRandomFileName());
+            Directory.CreateDirectory(logDir);
+            try
+            {
+                var paths = new Mock<IServerApplicationPaths>();
+                paths.Setup(p => p.LogDirectoryPath).Returns(logDir);
+
+                var logger = new ClientEventLogger(paths.Object);
+                using var contents = new MemoryStream(Encoding.UTF8.GetBytes("payload"));
+
+                var fileName = await logger.WriteDocumentAsync(clientName, clientVersion, contents);
+
+                var resolved = Path.GetFullPath(Path.Combine(logDir, fileName));
+                var rootWithSep = Path.GetFullPath(logDir) + Path.DirectorySeparatorChar;
+                Assert.StartsWith(rootWithSep, resolved, StringComparison.Ordinal);
+                Assert.True(File.Exists(resolved));
+            }
+            finally
+            {
+                Directory.Delete(logDir, recursive: true);
+            }
+        }
+    }
+}