WPBakery Page Builder Addons by Livemesh Stored Cross-Site Scripting Vulnerability

A stored cross-site scripting vulnerability has been identified in the WPBakery Page Builder Addons by Livemesh plugin for WordPress, affecting all versions through 3.9.4. The vulnerability arises from inadequate input sanitization and output escaping in the '[lvca_carousel]' and '[lvca_posts_carousel]' shortcode attributes. Shortcode attributes are encoded with 'wp_json_encode()' and then output into single-quoted 'data-settings' HTML attributes without proper escaping using 'esc_attr()'. This flaw allows authenticated attackers with Contributor-level access and above to inject arbitrary web scripts into pages, which are executed when a user accesses the modified page.

Impact

Exploitation of this vulnerability allows for stored cross-site scripting, where injected scripts are executed in the context of the user viewing the page.

Reproduction

To reproduce this vulnerability, an authenticated user with Contributor-level access or higher can use the '[lvca_carousel]' or '[lvca_posts_carousel]' shortcodes. When adding these shortcodes, the user can inject scripts into the 'data-settings' attribute by including single quotes, which are not properly escaped. Once the shortcode is saved, the injected script will execute whenever the page is viewed.