diff --git a/src/main.ts b/src/main.ts
index 60deb42..9d2ecc5 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -6919,9 +6919,24 @@ ipcMain.handle('open-folder', (_, folderPath: string) => {
     }
 });
 
+// Extensions that shell.openPath would happily execute via the system
+// default. Calc.exe via XSS smuggling is the canonical example; this
+// list blocks the obvious vectors. Media/text/image extensions are
+// still fine — shell.openPath opens them in the OS's default viewer.
+const OPEN_FILE_BLOCKED_EXTENSIONS = new Set([
+    '.exe', '.bat', '.cmd', '.com', '.ps1', '.vbs', '.vbe',
+    '.js', '.jse', '.wsf', '.wsh', '.scr', '.msi', '.msp',
+    '.lnk', '.cpl', '.reg', '.hta', '.jar', '.application'
+]);
+
 ipcMain.handle('open-file', async (_, filePath: string): Promise<boolean> => {
     if (typeof filePath !== 'string' || !filePath) return false;
     if (!fs.existsSync(filePath)) return false;
+    const ext = path.extname(filePath).toLowerCase();
+    if (OPEN_FILE_BLOCKED_EXTENSIONS.has(ext)) {
+        appendDebugLog('open-file-rejected-extension', { ext, path: filePath.slice(0, 200) });
+        return false;
+    }
     const result = await shell.openPath(filePath);
     // shell.openPath returns '' on success, an error string on failure.
     return result === '';