Stored XSS in Formidable Kinetic WordPress Plugin

Executive Summary

The Formidable Kinetic plugin for WordPress has a Stored Cross-Site Scripting (XSS) vulnerability in versions up to and including 1.1.01. This vulnerability arises because the plugin does not properly sanitize or escape user-supplied shortcode attributes such as 'window', 'class', and 'label' in the FrmKinetic::link() function. These attributes are directly inserted into HTML anchor tag attributes, allowing an authenticated attacker with contributor-level access or higher to inject malicious scripts that execute whenever a user views the affected page.

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Impact Analysis

This vulnerability can allow an attacker with contributor-level access or above to inject arbitrary web scripts into pages. These scripts execute in the context of users who visit the infected pages, potentially leading to theft of user credentials, session hijacking, defacement, or distribution of malware. Because the attack is stored, the malicious code persists on the site and affects all users who access the compromised content.

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Detection Guidance

Detection of this vulnerability involves identifying the presence of the Formidable Kinetic plugin version 1.1.01 or earlier on your WordPress installation.

Since the vulnerability is related to stored Cross-Site Scripting via the 'kinetic_link' shortcode, you can search your WordPress content for usage of this shortcode with suspicious or unexpected attributes.

Commands to help detect the vulnerability include:

• Use WP-CLI to list installed plugins and their versions: `wp plugin list`
• Search the WordPress database for posts containing the 'kinetic_link' shortcode: `wp db query "SELECT ID, post_content FROM wp_posts WHERE post_content LIKE '%[kinetic_link%'"`
• Manually inspect the shortcode attributes in the content for suspicious script injections or unusual HTML attribute values.

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Mitigation Strategies

Immediate mitigation steps include:

• Update the Formidable Kinetic plugin to a version later than 1.1.01 where the vulnerability is fixed.
• Restrict contributor-level and higher user permissions to trusted users only, as the vulnerability requires authenticated users with contributor access or above.
• Review and sanitize existing content that uses the 'kinetic_link' shortcode to remove any injected scripts.
• Implement Web Application Firewall (WAF) rules to detect and block attempts to exploit this stored XSS vulnerability.

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