Fix open redirects in TypeScript and Next.js
============================================

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

Page: https://softwaresecurity.com/fix/open-redirect/typescript-nextjs/

What is in this archive
-----------------------
open-redirect/typescript-nextjs/   the project: three implementations of the same code and one test suite
  lib/impl/vulnerable.ts   (vulnerable)
  lib/impl/fixed.ts   (fixed)
  lib/impl/wrong.ts   (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/typescript-nextjs 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/typescript-nextjs
    node run-all.mjs open-redirect/typescript-nextjs

Verified
--------
  11 October 2026 on macOS 27.0 (Darwin 27.0.0, arm64), with node 26.11.1, npm
  11.20.0, next 16.4.0, react 19.3.0, vitest 5.0.3 (Vite 8.3.4), typescript
  6.0.3, 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.
