diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index 157d3ed8..92578335 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -21,3 +21,7 @@
 **Vulnerability:** `CustomEmployeeManager.Register` accepted arbitrary employee IDs without validation, which were later used directly in `Path.Combine` to construct image loading paths, enabling path traversal (CWE-22).
 **Learning:** Identifiers provided by mods or external sources must be treated as untrusted input and validated before being used in file system operations.
 **Prevention:** Validate input strings that form part of a file path before concatenating them. Reject them if they contain directory traversal characters like `..`, `Path.DirectorySeparatorChar`, `Path.AltDirectorySeparatorChar`, or any invalid filename characters (using `Path.GetInvalidFileNameChars()`).
+## 2024-05-24 - Prevent Path Traversal via Arbitrary Identifiers
+**Vulnerability:** A path traversal vulnerability existed in `CustomEmployeeManager.SetPortrait` because arbitrary `employeeId` strings from mods were used in `Path.Combine` without being validated.
+**Learning:** Even when reading benign assets (like portraits), any string identifier that originates externally must be validated before being used to construct a file path.
+**Prevention:** Use `id.IndexOfAny(Path.GetInvalidFileNameChars()) >= 0 || id.Contains("..")` to validate these external identifiers rather than relying on directory or environment constraints alone.
diff --git a/src/API/CustomEmployeeManager.cs b/src/API/CustomEmployeeManager.cs
index 9b4512b6..a2d90821 100644
--- a/src/API/CustomEmployeeManager.cs
+++ b/src/API/CustomEmployeeManager.cs
@@ -891,10 +891,21 @@ private static void SetPortrait(Transform card, string employeeId)
 
             string assetsDir = Path.Combine(MelonEnvironment.UserDataDirectory, "ModAssets");
             string? imagePath = null;
-            foreach (var ext in new[] { ".jpg", ".png" })
+
+            // Prevent path traversal by validating the arbitrary employeeId string
+            bool isSafePath = employeeId.IndexOfAny(Path.GetInvalidFileNameChars()) < 0 && !employeeId.Contains("..");
+
+            if (isSafePath)
+            {
+                foreach (var ext in new[] { ".jpg", ".png" })
+                {
+                    string candidate = Path.Combine(assetsDir, employeeId + ext);
+                    if (File.Exists(candidate)) { imagePath = candidate; break; }
+                }
+            }
+            else
             {
-                string candidate = Path.Combine(assetsDir, employeeId + ext);
-                if (File.Exists(candidate)) { imagePath = candidate; break; }
+                CrashLog.Log($"[Security] Prevented path traversal attempt in SetPortrait for employeeId: {employeeId}");
             }
 
             if (imagePath != null)