diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index 8f4c12e..6413106 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -13,3 +13,8 @@
 **Learning:** When dealing with structured text files where line breaks determine the structure (like `.env`, `ini`, or CSV files), user input MUST be explicitly stripped of all newline characters (`\r` and `\n`) before interpolation. Relying only on `trim()` is insufficient as it only removes whitespace at the boundaries, not within the payload.
 
 **Prevention:** Sanitize all user input destined for line-based configuration files by explicitly stripping `\r` and `\n` characters (e.g., using `str_replace(["\r", "\n"], '', $value)` in PHP) to ensure the input remains strictly on a single line.
+
+## 2024-05-25 - Path Validation Bypass (Directory Traversal)
+**Vulnerability:** In `validatePath` and `isValidProjectPath` across multiple API files (`files.php`, `terminal.php`, `projects.php`, `src/Utils/Security.php`), the code used `strpos($realPath, $allowedReal) === 0` to check if a user-supplied path was within an allowed directory.
+**Learning:** This is a classic path traversal bypass in PHP. Because it only checks for a string prefix, an allowed path like `/var/www` will successfully match a malicious sibling directory like `/var/www_backup` or `/var/www-secret`.
+**Prevention:** Always append a trailing directory separator (`/`) to the allowed path prefix before checking with `strpos`, or perform an exact match if the paths are identical. For example: `strpos($realPath, rtrim($allowedReal, '/') . '/') === 0`.
diff --git a/public/api/files.php b/public/api/files.php
index 5f1d876..915610c 100644
--- a/public/api/files.php
+++ b/public/api/files.php
@@ -120,9 +120,19 @@ function validatePath($path, $allowedPaths) {
     $isValid = false;
     foreach ($allowedPaths as $allowed) {
         $allowedReal = realpath($allowed);
-        if ($allowedReal && strpos($realPath, $allowedReal) === 0) {
-            $isValid = true;
-            break;
+        if ($allowedReal) {
+            if ($realPath === $allowedReal) {
+                $isValid = true;
+                break;
+            }
+
+            $normalizedReal = str_replace('\\', '/', $realPath);
+            $normalizedAllowed = rtrim(str_replace('\\', '/', $allowedReal), '/') . '/';
+
+            if (strpos($normalizedReal, $normalizedAllowed) === 0) {
+                $isValid = true;
+                break;
+            }
         }
     }
     
diff --git a/public/api/projects.php b/public/api/projects.php
index 5f915e4..3eac660 100644
--- a/public/api/projects.php
+++ b/public/api/projects.php
@@ -1181,8 +1181,17 @@ function isValidProjectPath($path, $workspaces) {
     
     foreach ($workspaces as $ws) {
         $wsPath = realpath($ws['path']);
-        if ($wsPath && strpos($realPath, $wsPath) === 0) {
-            return true;
+        if ($wsPath) {
+            if ($realPath === $wsPath) {
+                return true;
+            }
+
+            $normalizedReal = str_replace('\\', '/', $realPath);
+            $normalizedAllowed = rtrim(str_replace('\\', '/', $wsPath), '/') . '/';
+
+            if (strpos($normalizedReal, $normalizedAllowed) === 0) {
+                return true;
+            }
         }
     }
     
diff --git a/public/api/terminal.php b/public/api/terminal.php
index 155b6a3..a8cdaf3 100644
--- a/public/api/terminal.php
+++ b/public/api/terminal.php
@@ -124,9 +124,19 @@ function validatePath($path, $allowedPaths) {
     $isValid = false;
     foreach ($allowedPaths as $allowed) {
         $allowedReal = realpath($allowed);
-        if ($allowedReal && strpos($realPath, $allowedReal) === 0) {
-            $isValid = true;
-            break;
+        if ($allowedReal) {
+            if ($realPath === $allowedReal) {
+                $isValid = true;
+                break;
+            }
+
+            $normalizedReal = str_replace('\\', '/', $realPath);
+            $normalizedAllowed = rtrim(str_replace('\\', '/', $allowedReal), '/') . '/';
+
+            if (strpos($normalizedReal, $normalizedAllowed) === 0) {
+                $isValid = true;
+                break;
+            }
         }
     }
     
diff --git a/src/Utils/Security.php b/src/Utils/Security.php
index fc334dd..833cc01 100644
--- a/src/Utils/Security.php
+++ b/src/Utils/Security.php
@@ -45,8 +45,17 @@ public static function validateFilePath(string $path, array $allowedPaths): ?str
         
         foreach ($allowedPaths as $allowedPath) {
             $realAllowedPath = realpath($allowedPath);
-            if ($realAllowedPath && strpos($realPath, $realAllowedPath) === 0) {
-                return $realPath;
+            if ($realAllowedPath) {
+                if ($realPath === $realAllowedPath) {
+                    return $realPath;
+                }
+
+                $normalizedReal = str_replace('\\', '/', $realPath);
+                $normalizedAllowed = rtrim(str_replace('\\', '/', $realAllowedPath), '/') . '/';
+
+                if (strpos($normalizedReal, $normalizedAllowed) === 0) {
+                    return $realPath;
+                }
             }
         }