Advisory

Yorick Koster, July 2016

Stored Cross-Site Scripting in WP Canvas - Shortcodes WordPress Plugin

Abstract

A Cross-Site Scripting vulnerability was found in the WP Canvas - Shortcodes WordPress Plugin. This issue allows an attacker to perform a wide variety of actions, such as stealing Administrators' session tokens, or performing arbitrary actions on their behalf. This issue can be exploited by authenticated users with the Contributor or higher role.

OVE ID

OVE-20160724-0031

Tested versions

This issue was successfully tested on WP Canvas - Shortcodes WordPress Plugin version 1.92.

Fix

This issue has been addressed in WP Canvas - Shortcodes WordPress Plugin version 2.07.

Introduction

The WP Canvas - Shortcodes WordPress Plugin provides a number of shortcodes that can be used in a WordPress post or page. A Cross-Site Scripting vulnerability was found in the WP Canvas - Shortcodes WordPress Plugin. This issue allows an attacker to perform a wide variety of actions, such as stealing Administrators' session tokens, or performing arbitrary actions on their behalf. This issue can be exploited by authenticated users with the Contributor or higher role.

Details

This issue exists due to the lack of validation on the url attributed of the wc_button shortcode. A Contributor or higher can create a button with a specially crafted Javascript payload. When a (logged) on user clicks on this button, the payload will be executed. This bypasses the unfiltered_html privilege of WordPress, which is normally only assigned to Editors & Administrators.

Proof of concept

[wc_button type="primary" url="javascript:alert(1)" title="Visit Site" target="self" position="float"]Sample Content[/wc_button]

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