In general, while we try our best to write secure JavaScript code, we must recognize that the JavaScript code that we write will eventually be sent to a browser. With the existence of XSS/CSRF, code on the browser can be manipulated fairly easily, as you saw in the previous chapter.
We will start off with a simple application, where we attempt to create a user, similar to many of the apps we are familiar with, albeit a more simplified one.
We will walk through the creation of the app, use it, and then utilize it again under modified circumstances where the trust actually gets misplaced.
This example is based on Tornado/Python. You can easily recreate this example using Express.js/Node.js. The important things to note here are the issues happening on the client side.
What we are going to code in this section is a simple user creation form, which sends the values to the backend/server side. On the client side, we are going to use JavaScript to prevent...