CVE-2025-26545: Related Posts Plugin CSRF Vulnerability

CVE-2025-26545 Overview

CVE-2025-26545 is a Cross-Site Request Forgery (CSRF) vulnerability in the "Related Posts Line-up-Exactly by Milliard" WordPress plugin (slug: related-posts-line-up-exactry-by-milliard) that allows attackers to chain the CSRF with Stored Cross-Site Scripting (XSS). This vulnerability enables attackers to trick authenticated administrators into unknowingly submitting malicious requests that inject persistent JavaScript code into the WordPress site.

Critical Impact

Attackers can leverage CSRF to inject malicious scripts that persist in the WordPress database, potentially compromising all site visitors and administrators through Stored XSS payloads.

Affected Products

• Related Posts Line-up-Exactly by Milliard plugin version 0.0.22 and earlier
• WordPress installations running vulnerable versions of the plugin
• All sites with the plugin installed where administrative users can be targeted

Discovery Timeline

• 2025-02-13 - CVE-2025-26545 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-26545

Vulnerability Analysis

This vulnerability combines two distinct attack vectors: Cross-Site Request Forgery (CSRF) and Stored Cross-Site Scripting (XSS). The plugin fails to properly implement CSRF protections (such as nonce verification) on administrative forms that handle user-supplied input. Additionally, the input is not adequately sanitized before being stored in the database and subsequently rendered to users, enabling the Stored XSS component.

The attack chain works as follows: an attacker crafts a malicious page or link containing a forged request that, when visited by an authenticated WordPress administrator, submits data to the vulnerable plugin endpoint. Because no CSRF token validation occurs, the request is accepted. The submitted data contains JavaScript payloads that are stored and later executed in the browsers of users viewing the affected content.

Root Cause

The root cause is CWE-352 (Cross-Site Request Forgery), where the plugin does not verify that form submissions originate from legitimate user actions. WordPress provides built-in CSRF protection through nonces (wp_nonce_field() and wp_verify_nonce()), but these mechanisms are not implemented in the affected plugin endpoints. This lack of verification, combined with insufficient output encoding, creates the CSRF-to-Stored-XSS attack chain.

Attack Vector

The attack is network-based and requires user interaction—specifically, an authenticated administrator must be tricked into visiting a malicious page while logged into WordPress. The attacker does not need any privileges on the target system. Upon successful exploitation, the scope changes as the stored XSS payload can affect other users who view the compromised content.

The attack sequence typically involves:

1. Attacker identifies a vulnerable endpoint in the plugin's settings or configuration page
2. Attacker crafts an HTML page with an auto-submitting form targeting the vulnerable endpoint
3. Administrator is lured to visit the attacker's malicious page (via phishing, social engineering, or malicious advertisements)
4. The form automatically submits, storing the XSS payload in the WordPress database
5. Any user viewing pages where the plugin renders content executes the stored malicious script

Detection Methods for CVE-2025-26545

Indicators of Compromise

• Unexpected JavaScript code or <script> tags appearing in plugin configuration or related posts output
• Suspicious administrator activity or settings changes that were not intentionally made
• Browser console errors or unexpected network requests originating from the WordPress admin area
• Audit logs showing configuration changes without corresponding legitimate user sessions

Detection Strategies

• Review WordPress database tables associated with the Related Posts Line-up-Exactly by Milliard plugin for unexpected HTML/JavaScript content
• Implement Content Security Policy (CSP) headers to detect and block inline script execution
• Monitor web application firewall (WAF) logs for requests containing XSS patterns targeting plugin endpoints
• Conduct regular code audits of plugin settings and stored content for malicious payloads

Monitoring Recommendations

• Enable WordPress audit logging plugins to track administrative actions and configuration changes
• Configure alerting for any changes to plugin settings outside of scheduled maintenance windows
• Implement browser-based XSS protection mechanisms and monitor for CSP violation reports
• Review referrer headers in server logs to identify suspicious cross-origin form submissions

How to Mitigate CVE-2025-26545

Immediate Actions Required

• Deactivate and remove the Related Posts Line-up-Exactly by Milliard plugin until a patched version is available
• Audit all content rendered by the plugin for signs of injected malicious scripts
• Review WordPress administrator accounts for unauthorized sessions or recent suspicious activity
• Implement a Web Application Firewall (WAF) rule to block requests containing common XSS payloads

Patch Information

As of the published information, versions through 0.0.22 are affected. Site administrators should check for updates from the plugin developer. Review the Patchstack vulnerability database entry for the latest remediation guidance and patch availability.

Workarounds

• Remove or deactivate the plugin entirely until a patched version becomes available
• Restrict access to the WordPress admin panel using IP allowlisting
• Implement additional authentication factors for WordPress administrative users
• Use security plugins that add CSRF protection layers to forms across the WordPress installation

# Deactivate the vulnerable plugin via WP-CLI
wp plugin deactivate related-posts-line-up-exactry-by-milliard --allow-root

# Optionally remove the plugin completely
wp plugin delete related-posts-line-up-exactry-by-milliard --allow-root

# Scan for potential XSS payloads in options table
wp db search "<script" wp_options --allow-root