Background

Clickjacking, also known as a "UI redress attack", is when an attacker uses multiple transparent or opaque layers to trick a user into clicking on a button or link on another page when they were intending to click on the the top level page. Thus, the attacker is "hijacking" clicks meant for their page and routing them to another page, most likely owned by another application, domain, or both.

Using a similar technique, keystrokes can also be hijacked. With a carefully crafted combination of stylesheets, iframes, and text boxes, a user can be led to believe they are typing in the password to their email or bank account, but are instead typing into an invisible frame controlled by the attacker.

• OWASP Clickjacking

One way to defend against clickjacking is to include a "frame-breaker" script in each page that should not be framed. The following methodology will prevent a webpage from being framed even in legacy browsers, that do not support the X-Frame-Options-Header.

• OWASP Clickjacking Defense Cheat Sheet

What this library does

ember-anti-clickjacking adds some JavaScript that runs before the application boots and prevents it from being rendered within the context of another page.

Is this all I need?

No! Defense in depth is important for protecting against clickjacking because of variations among browsers.

You should also be setting an appropriate X-Frame-Options header. If there are no cases in which your application can be embedded, the safest thing to do is deny framing altogether:

X-Frame-Options: DENY

If you're using a Content Security Policy (and you should be!), you should also set an appropriate frame-ancestors list. To prevent embedding altogether, set it to "none":

Content-Security-Policy: frame-ancestors "none";

Options

By default, ember-anti-clickjacking will inject

<style id="antiClickjack">body{display:none !important;}</style>

into your index.html. This is a protection for some older browsers that allow attackers to clobber top.location. Unfortunately, it doesn't play well with <noscript>. If you're using a Content Security Policy, the <style> tag also requires the style-src 'unsafe-inline' directive.

You can turn off the injection of the <style> tag as follows:

// config/environment.js:

module.exports = function(environment) {
  var ENV = {
    'ember-anti-clickjacking': {
      style: false
    }
  }
  // ...
};