Fix open redirects in Node.js and Express
=========================================

Resolve next against your own origin with new URL(next, site), the WHATWG
parser browsers use, and redirect only if url.origin is in an exact allowlist
and the URL carries no user name or password; otherwise redirect to a fixed
page. Pass res.redirect the url.href you checked. Never trust startsWith('/')
or a host substring test.

Page: https://softwaresecurity.com/fix/open-redirect/node-express/

What is in this archive
-----------------------
open-redirect/node-express/   the project: three implementations of the same code and one test suite
  impl/vulnerable.js   (vulnerable)
  impl/fixed.js   (fixed)
  impl/wrong.js   (a plausible fix that still fails)
run-all.mjs   runs the tests in all three modes and checks the results (Node.js only)
LICENSE-CODE.txt

Run it
------
  Tested with Node.js 26.11.1; package.json allows Node.js ^22.23.2 || ^24.18.1
  || >=26.5.1. run-all.mjs needs Node.js 22 or later. Supported versions:
  https://softwaresecurity.com/fix/versions/

  From the open-redirect/node-express folder, install the dependencies once
  (this needs network access):

    npm ci

  Then run the tests. IMPL chooses the implementation the tests load:

    # every test passes
    IMPL=fixed npm test --silent
    # an exploit test fails
    IMPL=vulnerable npm test --silent
    # a test fails
    IMPL=wrong npm test --silent

  The JUnit report is written to reports/junit.xml. To run all three modes and
  check the results in one step, run the harness from this top folder (it needs
  only Node.js; --install runs the install step first):

    node run-all.mjs --install open-redirect/node-express
    node run-all.mjs open-redirect/node-express

Verified
--------
  11 October 2026 on macOS 27.0 (Darwin 27.0.0, arm64), with node 26.11.1, npm
  11.20.0, express 5.3.0, expressSession 1.19.0, semgrep 1.180.0. Versions and
  results hold for that date: run the tests with your own versions before
  relying on the fix.

Licence
-------
  The code is MIT licensed (LICENSE-CODE.txt). The page text is CC BY 4.0.
