CVE-2025-23989: Internal Link Builder CSRF Vulnerability

CVE-2025-23989 Overview

CVE-2025-23989 is a Cross-Site Request Forgery (CSRF) vulnerability in the Alessandro Piconi Internal Link Builder plugin for WordPress. The flaw affects all versions up to and including 1.0. According to the Patchstack advisory, the CSRF weakness chains into a stored Cross-Site Scripting (XSS) condition, allowing an attacker to persist malicious script content through a forged authenticated request. Exploitation requires user interaction, typically by tricking an authenticated administrator into visiting an attacker-controlled page. The vulnerability is tracked under [CWE-352].

Critical Impact

A successful CSRF-to-stored-XSS chain enables attackers to execute arbitrary JavaScript in the context of authenticated WordPress administrators, leading to session theft, account takeover, or persistent site compromise.

Affected Products

• Alessandro Piconi Internal Link Builder WordPress plugin (internal-link-builder)
• All versions from initial release through 1.0
• WordPress sites with the plugin installed and activated

Discovery Timeline

• 2025-01-31 - CVE-2025-23989 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-23989

Vulnerability Analysis

The Internal Link Builder plugin fails to validate the origin of state-changing HTTP requests. WordPress plugins must verify a nonce token on requests that modify plugin settings or stored data. This plugin omits or incorrectly implements that check, leaving its administrative endpoints reachable through forged requests.

The Patchstack advisory categorizes the issue as a CSRF chain leading to stored XSS. An attacker crafts a malicious page or email containing a hidden form that submits to the plugin's vulnerable endpoint. When an authenticated administrator loads that page, the browser sends the request with valid session cookies. The plugin processes the request and stores attacker-supplied content, which is later rendered to other users without proper output encoding.

Root Cause

The root cause is missing or insufficient CSRF protection [CWE-352] on plugin request handlers. WordPress provides wp_nonce_field() and check_admin_referer() primitives to bind requests to a user session, but the affected handlers do not enforce these checks. A secondary defect is missing output sanitization, which converts the CSRF condition into a persistent XSS payload.

Attack Vector

The attack vector is network-based with required user interaction. An attacker hosts a page containing a forged POST request targeting the WordPress administrator's site. The administrator must be authenticated and must visit the attacker-controlled page. No credentials or privileges are required from the attacker. The scope is changed because injected script executes in the WordPress administrative context, affecting users beyond the originally targeted account. See the Patchstack WordPress Vulnerability Advisory for the technical proof of concept.

Detection Methods for CVE-2025-23989

Indicators of Compromise

• Unexpected <script> tags, event handlers, or obfuscated JavaScript stored in Internal Link Builder configuration records within the WordPress database.
• WordPress administrator account activity originating from external Referer headers pointing to untrusted domains.
• Outbound requests from administrator browsers to unknown domains shortly after visiting third-party links.

Detection Strategies

• Inspect plugin option entries and post metadata for HTML or JavaScript content where only plain text is expected.
• Review WordPress access logs for POST requests to internal-link-builder admin endpoints missing the _wpnonce parameter.
• Correlate administrator login sessions with subsequent stored content changes that occur without corresponding admin UI navigation.

Monitoring Recommendations

• Enable WordPress audit logging to record plugin setting changes with timestamps, user IDs, and source IP addresses.
• Monitor browser-side telemetry for script execution within /wp-admin/ pages that references external domains.
• Alert on creation or modification of plugin options containing tags such as <script>, onerror=, or javascript:.

How to Mitigate CVE-2025-23989

Immediate Actions Required

• Deactivate and remove the Internal Link Builder plugin from all WordPress installations until a patched release is available.
• Audit the database for malicious content stored by the plugin and remove any injected scripts.
• Force a password reset and session invalidation for all WordPress administrator accounts.

Patch Information

At the time of NVD publication, no patched version above 1.0 has been identified in the available advisory data. Site operators should monitor the Patchstack WordPress Vulnerability Advisory and the plugin's WordPress.org listing for an updated release that implements check_admin_referer() and proper output escaping.

Workarounds

• Remove the plugin entirely if a patched version is not available, since CSRF flaws cannot be reliably mitigated through configuration alone.
• Deploy a Web Application Firewall (WAF) rule that blocks POST requests to plugin endpoints lacking a valid _wpnonce parameter.
• Restrict WordPress administrative access by IP allowlist and require administrators to use a separate, hardened browser profile when managing the site.

# Configuration example: remove the vulnerable plugin via WP-CLI
wp plugin deactivate internal-link-builder
wp plugin delete internal-link-builder

# Audit options table for stored script payloads
wp db query "SELECT option_name, option_value FROM wp_options WHERE option_value LIKE '%<script%' OR option_value LIKE '%onerror=%';"