diff --git a/QuickLook.Native/QuickLook.Native32/DOpus.cpp b/QuickLook.Native/QuickLook.Native32/DOpus.cpp
index eb1355e61..a31fafe37 100644
--- a/QuickLook.Native/QuickLook.Native32/DOpus.cpp
+++ b/QuickLook.Native/QuickLook.Native32/DOpus.cpp
@@ -26,11 +26,12 @@
 #define DOPUS_CLASS L"DOpus.ParentWindow"
 #define DOPUS_NAME L"Directory Opus"
 #define MSGWINDOW_CLASS L"QuickLook.Native.DOpus.MsgWindow"
+#define MAX_BUFFER_SIZE (10 * 1024 * 1024)  // 10MB limit for IPC data
 
 HWND hMsgWnd;
 HANDLE hGetResultEvent;
 
-PCHAR pXmlBuffer;
+PCHAR pXmlBuffer = nullptr;
 
 void DOpus::GetSelected(PWCHAR buffer)
 {
@@ -72,9 +73,12 @@ void DOpus::GetSelected(PWCHAR buffer)
 
     WaitForSingleObject(hGetResultEvent, 2000);
 
-    ParseXmlBuffer(buffer);
-
-    delete[] pXmlBuffer;
+    if (pXmlBuffer != nullptr)
+    {
+        ParseXmlBuffer(buffer);
+        delete[] pXmlBuffer;
+        pXmlBuffer = nullptr;
+    }
 }
 
 void DOpus::ParseXmlBuffer(PWCHAR buffer)
@@ -88,6 +92,9 @@ void DOpus::ParseXmlBuffer(PWCHAR buffer)
      *         ...
      */
 
+    if (pXmlBuffer == nullptr)
+        return;
+
     using namespace rapidxml;
 
     xml_document<> doc;
@@ -130,8 +137,21 @@ LRESULT CALLBACK DOpus::msgWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARA
     case WM_COPYDATA:
         {
             auto cds = reinterpret_cast<PCOPYDATASTRUCT>(lParam);
+            // Validate COPYDATASTRUCT and enforce reasonable size limit (10MB)
+            if (cds == nullptr || cds->lpData == nullptr || cds->cbData == 0 || cds->cbData > MAX_BUFFER_SIZE)
+            {
+                return 0;
+            }
+
             auto buf = static_cast<PCHAR>(cds->lpData);
 
+            // Clean up any previous buffer before allocating a new one
+            if (pXmlBuffer != nullptr)
+            {
+                delete[] pXmlBuffer;
+                pXmlBuffer = nullptr;
+            }
+
             pXmlBuffer = new CHAR[cds->cbData + 1]{'\0'};
             memcpy(pXmlBuffer, buf, cds->cbData);
 
diff --git a/QuickLook.Native/QuickLook.Native32/MultiCommander.cpp b/QuickLook.Native/QuickLook.Native32/MultiCommander.cpp
index 16ce94a71..0557ede33 100644
--- a/QuickLook.Native/QuickLook.Native32/MultiCommander.cpp
+++ b/QuickLook.Native/QuickLook.Native32/MultiCommander.cpp
@@ -46,6 +46,10 @@ void MultiCommander::GetSelected(PWCHAR buffer)
         return;
     }
 
+    if (pCurrentItemPath == nullptr) {
+        return;
+    }
+
     auto path = reinterpret_cast<PWCHAR>(pCurrentItemPath);
     wcscpy_s(buffer, wcslen(path) + 1, path);
 
@@ -84,8 +88,16 @@ LRESULT CALLBACK MultiCommander::msgWindowProc(HWND hWnd, UINT uMsg, WPARAM wPar
         case WM_COPYDATA:
         {
             delete[] pCurrentItemPath;
+            pCurrentItemPath = nullptr;
 
             auto cds = reinterpret_cast<PCOPYDATASTRUCT>(lParam);
+            // Validate COPYDATASTRUCT and enforce reasonable size limit (10MB)
+            if (cds == nullptr || cds->lpData == nullptr || cds->cbData == 0 || cds->cbData > MAX_BUFFER_SIZE)
+            {
+                SetEvent(hGetResultEvent);
+                return 0;
+            }
+
             auto buf = static_cast<PCHAR>(cds->lpData);
 
             pCurrentItemPath = new CHAR[cds->cbData + 1]{ '\0' };
diff --git a/QuickLook.Native/QuickLook.Native32/MultiCommander.h b/QuickLook.Native/QuickLook.Native32/MultiCommander.h
index 5279a3129..d6cdda128 100644
--- a/QuickLook.Native/QuickLook.Native32/MultiCommander.h
+++ b/QuickLook.Native/QuickLook.Native32/MultiCommander.h
@@ -19,6 +19,7 @@
 
 #define MULTICMD_CPF_GETCURITEMFULL 0x00000010L // Get full path of current item (file or folder) in focus
 #define MULTICMD_CPF_SOURCE         0x00000400L // Go to the new path in the source panel side
+#define MAX_BUFFER_SIZE             (10 * 1024 * 1024) // 10MB limit for IPC data
 
 #define MULTICMD_CLASS              L"MultiCommander MainWnd"
 #define MULTICMD_MSGWINDOW_CLASS    L"QuickLook.Native.MultiCmd.MsgWindow"
diff --git a/_codeql_detected_source_root b/_codeql_detected_source_root
new file mode 120000
index 000000000..945c9b46d
--- /dev/null
+++ b/_codeql_detected_source_root
@@ -0,0 +1 @@
+.
\ No newline at end of file