Stored XSS in bbPress Style Pack WordPress Plugin

Executive Summary

The bbp Style Pack plugin for WordPress has a Stored Cross-Site Scripting (XSS) vulnerability in versions up to and including 6.4.5. This occurs via the Topic Form Additional Fields feature because user input is not properly sanitized or escaped. Specifically, the function bsp_topic_fields_form_save() writes user input directly to post meta without filtering, and bsp_topic_content_append_topic_fields() outputs this data into HTML without escaping it. As a result, authenticated users with Subscriber-level access or higher who can create bbPress topics can inject malicious scripts that execute when any user views the affected page.

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Detection Guidance

This vulnerability involves stored Cross-Site Scripting (XSS) in the bbp Style Pack plugin for WordPress, specifically in versions up to and including 6.4.5. Detection involves checking for the presence of the vulnerable plugin version and inspecting the Topic Form Additional Fields for malicious script injections.

To detect if your system is vulnerable, first verify the installed version of the bbp Style Pack plugin. You can do this by running the following command in your WordPress installation directory:

• grep -i 'bbp_style_pack' wp-content/plugins/*/readme.txt

Alternatively, check the plugin version via the WordPress admin dashboard under Plugins.

To detect exploitation attempts or injected scripts, you can search the WordPress database for suspicious content in post meta fields related to bbp_topic_fields_label. For example, using WP-CLI:

• wp db query "SELECT meta_value FROM wp_postmeta WHERE meta_key LIKE 'bsp_topic_fields_label%' AND meta_value LIKE '%<script>%'"

Monitoring web server logs for unusual requests or payloads targeting topic creation forms may also help detect exploitation attempts.

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Impact Analysis

This vulnerability allows attackers with relatively low privileges (Subscriber-level and above) to inject arbitrary JavaScript into pages. When other users, including unauthenticated visitors, access these pages, the malicious scripts execute in their browsers. This can lead to theft of user credentials, session hijacking, defacement, or distribution of malware, compromising the security and integrity of the website and its users.

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Mitigation Strategies

The immediate mitigation step is to update the bbp Style Pack plugin to a version later than 6.4.5 where this vulnerability is fixed.

If an update is not immediately possible, consider temporarily disabling the Topic Form Additional Fields feature or restricting topic creation privileges to trusted users only.

Additionally, review and sanitize any existing post meta data that may contain malicious scripts injected via this vulnerability.

Implement web application firewall (WAF) rules to block suspicious input patterns related to this vulnerability.

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