Stockdio Historical Chart Cross-site Scripting

The Stockdio Historical Chart plugin before 2.8.1 for WordPress is affected by Cross Site Scripting (XSS) via stockdio_chart_historical-wp.js in wp-content/plugins/stockdio-historical-chart/assets/ because the origin of a postMessage() event is not validated. The stockdio_eventer function listens for any postMessage event. After a message event is sent to the application, this function sets the "e" variable as the event and checks that the types of the data and data.method are not undefined (empty) before proceeding to eval the data.method received from the postMessage. However, on a different website. JavaScript code can call window.open for the vulnerable WordPress instance and do a postMessage(msg,'*') for that object. (2021-01-19, CVE-2020-28707)

Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.

The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:

https://server.com/confirmation?message=Transaction+Complete

what results in:

<span>Confirmation: Transaction Complete</span>

In that case the message can be modified to become a valid Javascript code, e.g.:

https://server.com/confirmation?message=<script>dangerous javascript code here</script>

and it will be executed locally by the user's browser with full access to the user's personal application/browser data:

<span>Confirmation: <script>dangerous javascript code here</script></span>