Stored XSS in Sympl Repeater for ACF and Elementor WordPress Plugin

Executive Summary

The Sympl Repeater for ACF and Elementor plugin for WordPress has a Stored Cross-Site Scripting (XSS) vulnerability in all versions up to and including 2.3. This occurs because the plugin does not properly sanitize or escape input in the symp_arfe_replace_content() function. Specifically, it uses str_replace() to insert raw ACF repeater field values directly into Elementor-rendered HTML without escaping, allowing authenticated users with Author-level access or higher to inject malicious scripts that execute when other users view the affected pages.

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Impact Analysis

This vulnerability can allow attackers with Author-level access or above to inject arbitrary malicious scripts into web pages. These scripts will execute in the browsers of users who visit the injected pages, potentially leading to theft of user credentials, session hijacking, defacement, or other malicious actions. Because the vulnerability is a Stored Cross-Site Scripting issue, the malicious code persists on the site and affects all users who access the compromised content.

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Detection Guidance

This vulnerability involves Stored Cross-Site Scripting via ACF repeater field values in the Sympl Repeater for ACF and Elementor plugin for WordPress. Detection would involve identifying injected scripts within ACF repeater field content rendered by Elementor.

Since the vulnerability arises from insufficient input sanitization and output escaping in the symp_arfe_replace_content() function, detection can focus on scanning pages for suspicious or unexpected script tags or JavaScript code embedded in ACF repeater fields.

• Use WordPress database queries to search for suspicious script tags in the ACF repeater fields, for example, by querying the wp_postmeta table for meta values containing <script> tags.
• Example SQL command to find potential injected scripts in ACF repeater fields: SELECT * FROM wp_postmeta WHERE meta_value LIKE '%<script>%';
• Use web vulnerability scanners or custom scripts to crawl pages rendered by Elementor and look for reflected or stored XSS payloads.
• Monitor HTTP traffic for suspicious payloads or unexpected JavaScript code in responses from pages using the vulnerable plugin.

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Mitigation Strategies

Immediate mitigation steps include updating the Sympl Repeater for ACF and Elementor plugin to a version that fixes the vulnerability, if available.

If no patch is available, restrict Author-level and higher user permissions to trusted users only, as the vulnerability requires authenticated users with Author-level access or above to exploit.

Implement additional input sanitization and output escaping for ACF repeater field values in your WordPress environment to prevent script injection.

Consider disabling or removing the vulnerable plugin until a secure version is released.

Monitor your site for suspicious activity and injected scripts, and remove any malicious content found.

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