CVE-2025-48311: Invisible Optin CSRF Vulnerability

CVE-2025-48311 Overview

CVE-2025-48311 is a Cross-Site Request Forgery (CSRF) vulnerability in the OffClicks Invisible Optin WordPress plugin that enables attackers to chain the CSRF with Stored Cross-Site Scripting (XSS). This vulnerability allows unauthenticated attackers to trick authenticated administrators into submitting malicious requests that inject persistent JavaScript code into the plugin's settings or content areas.

Critical Impact

This CSRF-to-Stored-XSS chain allows attackers to persistently compromise WordPress sites, potentially leading to administrator account takeover, malware injection, and site defacement affecting all visitors.

Affected Products

• Invisible Optin WordPress Plugin version 1.0 and earlier
• WordPress installations using the invisible-optin plugin
• All users and administrators accessing affected WordPress sites

Discovery Timeline

• 2025-08-28 - CVE-2025-48311 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-48311

Vulnerability Analysis

The Invisible Optin plugin fails to implement proper CSRF protection mechanisms on forms and AJAX endpoints that handle plugin settings or user-submitted content. The absence of nonce verification allows attackers to craft malicious requests that, when executed by an authenticated administrator, store malicious JavaScript payloads directly in the WordPress database.

The attack is network-based and requires user interaction—specifically, an administrator must be tricked into visiting a malicious page or clicking a crafted link while authenticated to the WordPress admin panel. The scope is changed (S:C in CVSS vector), meaning the vulnerability impacts resources beyond its security scope, as the stored XSS payload executes in the browsers of all site visitors viewing affected pages.

Root Cause

The root cause is twofold: first, the plugin's form handlers lack proper CSRF token validation using WordPress nonces (wp_nonce_field() and wp_verify_nonce()). Second, user-supplied input is not properly sanitized before being stored in the database, and output encoding is missing when rendering stored content, enabling the Stored XSS component of this vulnerability chain.

Attack Vector

An attacker exploits this vulnerability by hosting a malicious HTML page containing an auto-submitting form that targets the vulnerable plugin endpoint. The form includes a JavaScript payload in one of the plugin's configurable fields. When an authenticated WordPress administrator visits the attacker's page, their browser automatically submits the form to the vulnerable endpoint using the administrator's active session cookies.

The malicious payload is stored in the WordPress database. Subsequently, when any user (including administrators) views pages where the Invisible Optin plugin renders content, the stored JavaScript executes in their browser context. This can be leveraged to steal session cookies, create rogue administrator accounts, modify site content, or redirect visitors to malicious sites.

Detection Methods for CVE-2025-48311

Indicators of Compromise

• Unexpected changes to Invisible Optin plugin settings or configuration
• JavaScript code present in plugin option values in the wp_options database table
• Suspicious <script> tags or JavaScript event handlers (e.g., onerror, onclick) in plugin-stored content
• Administrator activity logs showing settings changes without corresponding legitimate admin actions

Detection Strategies

• Monitor WordPress admin activity logs for unauthorized plugin settings modifications
• Implement Content Security Policy (CSP) headers to detect and block unauthorized inline script execution
• Scan WordPress database for suspicious script patterns in plugin-related options using security plugins like Wordfence or Sucuri
• Review server access logs for POST requests to plugin endpoints from unusual referrers

Monitoring Recommendations

• Enable WordPress audit logging to track all plugin configuration changes
• Configure web application firewall (WAF) rules to block requests containing common XSS payloads
• Set up alerts for any modifications to the invisible-optin plugin settings in the database
• Monitor client-side JavaScript errors that may indicate blocked XSS attempts

How to Mitigate CVE-2025-48311

Immediate Actions Required

• Deactivate and remove the Invisible Optin plugin (invisible-optin) immediately if version 1.0 or earlier
• Audit the wp_options table for any malicious script content stored by the plugin
• Review and revoke all administrator sessions and reset admin passwords
• Check for any unauthorized administrator accounts that may have been created
• Scan the entire WordPress installation for additional malware or backdoors

Patch Information

As of the last NVD update, the Invisible Optin plugin versions through 1.0 remain affected. Administrators should check the Patchstack vulnerability database for the latest patch status and any vendor remediation guidance. If no patch is available, consider migrating to an alternative optin/popup plugin with active security maintenance.

Workarounds

• Remove or deactivate the Invisible Optin plugin until a security patch is released
• Implement a Web Application Firewall (WAF) to filter malicious POST requests targeting the plugin
• Restrict WordPress admin panel access to trusted IP addresses only
• Use browser extensions like NoScript for administrators to prevent automatic form submissions

# Configuration example
# Deactivate plugin via WP-CLI
wp plugin deactivate invisible-optin

# Search for potentially malicious script content in wp_options
wp db query "SELECT option_name, option_value FROM wp_options WHERE option_value LIKE '%<script%' OR option_value LIKE '%onerror%' OR option_value LIKE '%javascript:%'"

# List all administrator users to verify no rogue accounts exist
wp user list --role=administrator --fields=ID,user_login,user_email,user_registered