Fix cross-site scripting in Node.js and Express
===============================================

Print every field through EJS's escaping tag <%= %>, which turns & < > " and '
into entities, and never through the raw tag <%- %>. For a link, escaping is
not enough: parse the URL with URL.parse and link only http and https, because
<%= %> leaves javascript:alert(1) working.

Page: https://softwaresecurity.com/fix/xss/node-express/

What is in this archive
-----------------------
xss/node-express/   the project: three implementations of the same code and one test suite
  views/profile/vulnerable.ejs   (vulnerable)
  views/profile/fixed.ejs   (fixed)
  views/profile/wrong.ejs   (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 xss/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 xss/node-express
    node run-all.mjs xss/node-express

Verified
--------
  11 October 2026, with node 26.11.1, express 5.3.0, ejs 6.0.1, parse5 8.0.1,
  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.
