Cross-Site Request Forgery to Stored XSS in jQuery Hover Footnotes WordPress Plugin

Executive Summary

The jQuery Hover Footnotes plugin for WordPress is vulnerable to Cross-Site Request Forgery (CSRF) in all versions up to and including 1.4. This vulnerability arises because the plugin's jqFootnotes_options_subpanel function lacks proper nonce validation. As a result, unauthenticated attackers can update the plugin's settings with arbitrary values.

These option values, such as jqfoot_anchor_open, jqfoot_anchor_close, and jqfoot_title, are echoed unescaped into the frontend page content. This allows the CSRF attack to be chained into a persistent Cross-Site Scripting (XSS) vulnerability affecting all site visitors if an attacker tricks a site administrator into performing an action like clicking a malicious link.

The overwritten option values are saved without sanitization and rendered unescaped on the frontend, enabling stored XSS.

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Impact Analysis

This vulnerability can allow an attacker to perform unauthorized changes to the plugin's settings via a forged request, potentially leading to persistent Cross-Site Scripting (XSS) attacks.

Such XSS attacks can affect all visitors to the site by injecting malicious scripts into frontend content, which can steal user data, hijack user sessions, or perform other malicious actions.

The attack requires tricking a site administrator into clicking a malicious link, which then causes the unauthorized changes.

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Detection Guidance

Detection of this vulnerability involves checking if the jQuery Hover Footnotes plugin for WordPress is installed and running a version up to and including 1.4.

Since the vulnerability is due to missing or incorrect nonce validation on the jqFootnotes_options_subpanel function, one way to detect exploitation attempts is to monitor for unexpected or unauthorized POST requests targeting the plugin's settings update endpoints.

You can use web server logs or network monitoring tools to look for suspicious requests that attempt to update plugin options without proper authentication.

Example commands to detect such activity might include:

• Using grep on web server logs to find POST requests related to the plugin: grep -i 'jqFootnotes_options_subpanel' /var/log/apache2/access.log
• Using curl to test if the plugin endpoint is accessible without proper nonce validation (requires knowledge of the endpoint URL): curl -X POST https://example.com/wp-admin/admin-ajax.php?action=jqFootnotes_options_subpanel

Additionally, scanning the WordPress installation to identify the plugin version can be done by checking the plugin files or using WP-CLI commands.

• wp plugin list --status=active | grep jquery-hover-footnotes

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Mitigation Strategies

Immediate mitigation steps include updating the jQuery Hover Footnotes plugin to a version later than 1.4 where the vulnerability is fixed.

If an update is not immediately available, consider temporarily disabling or uninstalling the plugin to prevent exploitation.

Additionally, restrict access to the WordPress admin area to trusted users only and educate administrators to avoid clicking on suspicious links that could trigger CSRF attacks.

Implementing Web Application Firewall (WAF) rules to block unauthorized POST requests to the plugin's settings endpoints can also help mitigate the risk.

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