IE No Open Middleware

1.1.1 verified Thu Apr 23 auth: no javascript maintenance

ienoopen is an Express-compatible middleware designed to enhance client-side security by setting the `X-Download-Options` HTTP header to `noopen`. This header, primarily relevant for Internet Explorer 8 and later, prevents users from directly opening downloaded HTML files in the browser's context, thereby mitigating certain types of HTML injection and cross-site scripting (XSS) attacks by forcing a "Save" action instead. The package is currently at version 1.1.1, with its last update over six years ago. It is considered to be in maintenance mode, as its standalone GitHub repository is archived, and its functionality has been integrated into the comprehensive `Helmet` security middleware suite, which includes `ienoopen` by default as `helmet.ieNoOpen()`. This package's narrow focus on a single, legacy IE-specific security header is its key differentiator, although its practical relevance has significantly diminished with modern browser adoption.

Common errors

error TypeError: ienoopen is not a function ↓

cause Attempting to use `app.use(ienoopen)` instead of invoking the middleware function `app.use(ienoopen())`.

fix

Ensure you call ienoopen() to get the middleware function: app.use(ienoopen());

error Error: Cannot find module 'ienoopen' ↓

cause The package `ienoopen` has not been installed or there's a typo in the import/require path.

fix

Install the package using npm: npm install ienoopen or yarn: yarn add ienoopen. Double-check the import/require statement for typos.

Warnings

deprecated The `X-Download-Options` header, which this package sets, is an unofficial header primarily implemented by Internet Explorer 8+. Modern browsers like Chrome, Firefox, and Safari do not support this header, making its security benefits largely irrelevant for contemporary web development. ↓

fix For broader security, consider using a comprehensive security middleware like Helmet, which includes this functionality (as `helmet.ieNoOpen()`) along with other critical headers for modern browsers.

gotcha The standalone `ienoopen` package is no longer actively maintained, and its GitHub repository is archived. While functional, no further updates or bug fixes are expected for this standalone module. ↓

fix Prefer using the `Helmet` middleware suite (`app.use(helmet())` or `app.use(helmet.ieNoOpen())`) if you still require this specific header alongside other modern security protections.

gotcha The `X-` prefix for HTTP headers (e.g., `X-Download-Options`) has been deprecated. While still understood by older systems, new headers should avoid this convention. ↓

fix No direct fix within this package, as it's designed to set a specific, legacy header. Be aware that this header pattern is outdated.

Install

npm install ienoopen

yarn add ienoopen

pnpm add ienoopen

Imports

ienoopen
wrong
```
import { ienoopen } from 'ienoopen';
```
correct
```
import ienoopen from 'ienoopen';
```
The package exports a default function. Do not use named imports.
ienoopen
```
const ienoopen = require('ienoopen');
```
CommonJS `require` syntax as shown in the original README.
ienoopen.d.ts
```
import type { RequestHandler } from 'express';
```
The `ienoopen` package ships its own types, but the middleware function itself aligns with Express's `RequestHandler`. No specific types are exported by `ienoopen` beyond its default function.

Quickstart

Sets up an Express server and applies the `ienoopen` middleware to set the `X-Download-Options` header. It also includes an example route that serves a downloadable HTML file to demonstrate the header's purpose in preventing direct execution in IE.

import express from 'express';
import ienoopen from 'ienoopen';

const app = express();
const port = 3000;

// Apply the ienoopen middleware
// This sets the 'X-Download-Options: noopen' header
app.use(ienoopen());

app.get('/', (req, res) => {
  res.send('Hello World! X-Download-Options header set.');
});

app.get('/download-unsafe-html', (req, res) => {
  res.setHeader('Content-Type', 'text/html');
  res.setHeader('Content-Disposition', 'attachment; filename="malicious.html"');
  // In older IE, without X-Download-Options: noopen, this could be opened directly.
  res.send('<html><body onload="alert(\'Malicious script executed in site context!\')"><h1>Untrusted content</h1></body></html>');
});

app.listen(port, () => {
  console.log(`Server listening at http://localhost:${port}`);
  console.log('Check response headers for X-Download-Options: noopen on relevant routes.');
});