Nom du plugin	Redirection for Contact Form 7
Type of Vulnerability	PHAR deserialization vulnerability
CVE Number	CVE-2025-8289
Urgence	Haut
CVE Publish Date	2025-08-19
Source URL	CVE-2025-8289

Urgent: PHP Object Injection in ‘Redirection for Contact Form 7’ (<= 3.2.4) — What WordPress Site Owners Need to Do Right Now

Auteur: WP-Firewall Security Team
Date: 2025-08-20
Mots clés: WordPress, WAF, Vulnerability, PHP Object Injection, Contact Form 7, Security

Résumé: A high-severity PHP Object Injection vulnerability (CVE-2025-8289, CVSS 7.5) affecting Redirection for Contact Form 7 versions ≤ 3.2.4 allows unauthenticated attackers to trigger PHAR deserialization and potentially achieve remote code execution, data access, or site compromise. Update to 3.2.5 immediately and follow the layered mitigations below.

Why this matters (short version)

A new vulnerability has been disclosed in the widely used “Redirection for Contact Form 7” plugin that permits unauthenticated PHP Object Injection (POI) via PHAR deserialization. Because the issue is unauthenticated and the plugin is popular, this is a high-risk problem that can — in the presence of a gadget chain — be turned into code execution, file read/write, or other impactful attacks. Exploit attempts are likely to be automated and widespread. If your site runs this plugin and is not updated or mitigated, treat it as urgent.

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What is PHP Object Injection via PHAR deserialization?

A short non-academic explanation:

• PHP object injection (POI) happens when an application unserializes user-controlled data that contains serialized PHP objects. When PHP reconstructs objects, their magic methods (e.g., __wakeup, __destruct) may run and can be abused if those classes perform sensitive actions (file operations, eval, database queries, etc.).
• PHAR deserialization is an attack technique where an attacker uploads or references a PHAR archive (or otherwise causes code to open a file with the phar:// stream wrapper). When PHP reads a PHAR archive, the archive’s metadata can contain serialized objects. PHP will deserialize that metadata, potentially causing object injection even when the application wasn’t explicitly calling unserialize() on user input.
• Combined, an attacker can craft a PHAR payload such that when the application loads the archive (or interacts with a file/resource that resolves to a PHAR) PHP performs an unsafe deserialization path, invoking dangerous behaviors.

What makes this vulnerability especially dangerous:

• The plugin endpoint is triggerable without authentication (any guest can attempt requests).
• PHAR deserialization may allow attackers to exploit built-in classes or plugin/theme code that has “gadget chains” — sequences of magic methods and object properties that lead to arbitrary actions.
• Once code execution or file write access is achieved, attackers commonly plant backdoors, create admin users, or steal data.

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The CVE and technical facts

• CVE: CVE-2025-8289
• Affected software: Redirection for Contact Form 7 plugin — versions ≤ 3.2.4
• Corrigé dans : version 3.2.5
• Gravité: High (CVSS 7.5)
• Privilège requis : Non authentifié
• Reported: 19 August 2025
• Exploit vector: PHAR deserialization causing PHP Object Injection

Patch or mitigate immediately. Treat all websites with the vulnerable plugin as at risk until remediated.

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Who should read this right now?

• WordPress admins and site owners using Contact Form 7 and Redirection for Contact Form 7
• Managed WordPress providers and hosting security teams
• Security teams that manage vulnerability and patch programs
• Any organization treating their WordPress install as part of an internet-facing asset inventory

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Immediate actions (what to do in the next hour)

1. Identify affected sites
   • Log into each WordPress site and go to Plugins → Installed Plugins.
   • Look for “Redirection for Contact Form 7” and confirm the installed version. If you have many sites, use WP-CLI:

     wp plugin list --field=name,version | grep -i wpcf7-redirect

   • Inventory all sites that have the plugin with version ≤ 3.2.4.
2. Update the plugin now
   • The vendor released version 3.2.5 which fixes the issue. Update via WP admin or WP-CLI:

     wp plugin update wpcf7-redirect

   • If you cannot update immediately (maintenance windows, compatibility checks), apply the temporary mitigations below.
3. Put hosts into a safe state
   • If you detect active exploitation (suspicious PHP files, admin accounts added, obfuscated files), disconnect public access or place a maintenance page while investigating.
4. Enable WAF/virtual patching (if available)
   • Configure your Web Application Firewall to block known exploit patterns for this vulnerability. (See sample rules below.)
5. Scan for compromise
   • Run a deep malware scan, check modified timestamps, scan for PHP webshells, and verify database integrity and user accounts.

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Recommended mitigations (short–medium–long term)

Layered defense is essential. Don’t rely on a single measure.

1. Patch (primary / permanent)
   • Update plugin to 3.2.5 or later. This is the only complete and supported fix.
2. Virtual patching / WAF rules (temporary / immediate)
   • Block requests containing use of the phar:// stream wrapper or requests that attempt to upload .phar fichiers.
   • Rate-limit or block suspicious POSTs to the plugin endpoints if possible.
   • Add specific rules to reject requests containing suspicious serialized object payloads when detected in bodies/fields.
3. Prevent unsafe file handling
   • Ensure file upload protections prevent .phar uploads and validate MIME types.
   • Restrict directories where uploads are stored and disallow PHP execution in those directories (e.g., disable PHP execution in wp-content/uploads).
4. PHP configuration hardening
   • Ensure phar.readonly = 1 (default on most environments). This reduces the risk of creating or modifying phar archives on the server.
   • Keep PHP and webserver up to date.
   • Do NOT enable insecure fichier php.ini settings to “work around” the issue; use the plugin update and WAF.
5. Permissions & least privilege
   • Run PHP-FPM processes and file system permissions with least privilege.
   • Restrict writable locations and database access scopes for web processes.
6. Monitor and audit
   • Monitor webserver logs for unusual patterns (detailed detection heuristics below).
   • Check file integrity regularly (compare to known-good copies) and verify recent edits.

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Detection — how to tell if someone tried or succeeded

Look for the following indicators in logs and the filesystem. None of these alone prove a successful exploit, but they indicate attempted or active abuse:

• Webserver access logs: Requests containing “phar://” in the request URI, query string, or request body.
• Upload endpoints receiving files with .phar extensions or with uncommon MIME types: application/x-phar, application/octet-stream avec .phar filename.
• POSTs that include long serialized strings (strings that start with O: ou s: and many colons/braces), particularly in fields that normally do not include serialized data.
• Unexpected creation or modification of PHP files under wp-content/uploads, Contenu wp/plugins, ou wp-content/thèmes.
• New admin users created, or unauthorized changes to user roles.
• Scheduled tasks (WP-Cron) that were not intentionally created.
• Outbound connections to suspicious domains immediately after plugin interaction.
• Base64-encoded content in plugin data or database options where none existed previously.
• Known webshell signatures detected by malware scanner (e.g., files with obfuscated code, eval(base64_decode())).

Suggested detection commands:

• Search for phar mentions:

  grep -R "phar://" /var/www/html -n

• Search for suspicious serialized payloads:

  grep -R "O:[0-9]\+:" /var/www/html -n

• Check for modified files in recent days:

  find /var/www/html -type f -mtime -7 -ls

If you find suspicious files, preserve logs and create a forensic copy before making changes.

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Example WAF rules and server-level mitigations

Below are sample rules you can apply quickly. Test in detection mode first to avoid false positives.

Nginx (block URIs containing phar://):

# Deny any request containing phar:// in the URL or query string
if ($request_uri ~* "phar://") {
    return 403;
}

Apache (.htaccess) — block upload of .phar files and phar wrappers:

# Block direct requests with phar:// pattern in the request
<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{THE_REQUEST} phar:// [NC]
  RewriteRule .* - [F]
</IfModule>

# Deny access to any .phar files
<FilesMatch "\.phar$">
  Order allow,deny
  Deny from all
</FilesMatch>

ModSecurity rule (example):

SecRule REQUEST_HEADERS|REQUEST_BODY "phar://" "id:1001001,phase:2,deny,log,msg:'Blocked phar wrapper attempt'"
SecRule FILES_NAMES|REQUEST_BODY "\.phar$" "id:1001002,phase:2,deny,log,msg:'Blocked PHAR upload attempt'"

WordPress (PHP) best-effort block inside a mu-plugin (temporary mitigation):

This code attempts to detect phar wrapper usage in request payload or uploaded files and block further processing. Place in wp-content/mu-plugins/ temporarily (test before deploying to production).

<?php
// MU plugin: block obvious PHAR attempts. Temporary measure.
add_action('init', function() {
    $blocked = false;
    // Check raw request body
    $raw = file_get_contents('php://input');
    if (stripos($raw, 'phar://') !== false) $blocked = true;
    // Check uploaded filenames
    foreach ($_FILES as $f) {
        if (!empty($f['name']) && stripos($f['name'], '.phar') !== false) $blocked = true;
    }
    if ($blocked) {
        header('HTTP/1.1 403 Forbidden');
        exit('Forbidden');
    }
}, 0);

Note: This is a defensive, temporary stopgap. It cannot replace a proper patch and can cause false positives. Remove once plugin updated.

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Post-exploitation checklist — if you suspect compromise

If you find indicators of successful exploitation, treat the site as potentially compromised and follow this priority checklist:

1. Take offline or present maintenance page (if necessary), but preserve logs and a forensic image.
2. Change passwords and rotate secrets:
   • WordPress admin passwords.
   • Hosting control panel, FTP/SFTP, SSH credentials.
   • Any API keys used by the site (mail providers, payment processors, CDN).
3. Run a full malware scan and manual code review:
   • Look for webshells, obfuscated PHP, unexpected scheduled tasks, or database options with injected content.
4. Restore from a clean backup (if available) from before the compromise.
   • Ensure plugin versions are updated before bringing the site back online.
5. If no clean backup, rebuild the site and import content only after thorough sanitization.
6. Review and remove unrecognized admin users, plugins, and themes.
7. Audit access logs to identify attacker IPs and method of entry; block and harden accordingly.
8. Implement monitoring (file integrity, login alerts, WAF logs).
9. Consider a professional incident response service for forensic analysis if the site is critical or if the breach appears complex.

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How attackers typically weaponize PHP Object Injection

• Weaponization often begins with a probe: attackers send test requests to endpoints that handle files or external resources. If an application uses file_get_contents or other file operations on attacker-controlled input, attackers attempt to substitute a PHAR archive or a path which triggers the phar:// wrapper.
• If the application or environment contains classes with unsafe magic methods, the serialized metadata will be deserialized and the malicious object chain activated.
• Once code execution is available, attackers will:
  • Upload a persistent backdoor (webshell) to an uploads folder or plugin file.
  • Create an admin user for persistent access.
  • Exfiltrate database contents.
  • Set up scheduled tasks.
  • Pivot to other systems if credentials are reused.

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Why a WAF / Virtual Patching helps — and what it can’t do

A Web Application Firewall is a useful, fast-response layer that can block exploit attempts before they reach vulnerable code. Effective WAF rules can:

• Detect and block known exploit patterns (phar://, suspicious serialized payloads).
• Block known malicious IPs and rate-limit suspicious traffic.
• Provide temporary virtual patches until the plugin is updated.

What a WAF cannot do:

• Replace the vendor-supplied security fix. If a vulnerability exists in PHP or the application, the only complete remediation is to patch the vulnerable code.
• Be 100% accurate — complex, novel exploits can bypass naive rules and false positives can block legitimate traffic.

That’s why we recommend patch + WAF + monitoring as a combined approach.

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How to validate you’re safe after updating

After you update Redirection for Contact Form 7 to 3.2.5, take these verification steps:

1. Confirm plugin version:
   • WordPress admin → Plugins or
   • wp plugin list | grep wpcf7-redirect
2. Clear caches (object cache, CDN) and the browser cache.
3. Re-scan for malware and integrity:
   • Run a file integrity comparison against fresh plugin and theme packages.
   • Scan for inserted webshells and suspicious files.
4. Monitor logs for repeated exploit attempts:
   • Even after patching, attackers may continue to probe; monitor for phar:// attempts and IPs.
5. Rotate keys and credentials if evidence suggests compromise.

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Practical developer notes (for plugin/theme authors)

If you are a developer, take away these best practices:

• Avoid unserialize() on untrusted input. Use JSON instead for external data.
• Never call file handling functions on user-controlled URIs without strict validation.
• Be aware of PHAR stream wrapper and how certain file operations can lead to deserialization of metadata.
• Implement input validation and sanitization at the earliest entry point.
• Hardening code to operate securely under the principle of least privilege makes exploitation harder.
• Keep third-party libraries and dependencies up to date.

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Example incident timeline (what to expect during an active outbreak)

• T0: Vulnerability disclosed publicly. Automated scanner signatures begin circulating within hours.
• T1 (0–24 hours): Mass scanning of the internet. Many high-volume bots will attempt to probe for phar:// and known endpoints.
• T2 (24–72 hours): Automated exploit scripts may attempt to upload payloads or craft PHAR payloads to trigger deserialization. Some attacks will succeed only where gadget chains exist.
• T3 (>72 hours): Attackers establishing persistence (webshells, admin accounts). Clean-up becomes more time-consuming.
• Recommended response: Patch within 24 hours and enable WAF rules immediately.

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Frequently asked questions (FAQ)

Q: My site doesn’t use the redirection features — is it still vulnerable?
A: Possibly. The vulnerability is in the plugin code itself and can be triggered by unauthenticated requests in many cases. If the plugin is installed and active, assume it’s vulnerable until updated.

Q: I can’t update immediately due to compatibility testing — what should I do?
A: Enable WAF/virtual patching to block exploit patterns, implement temporary server-side rules to reject phar:// usage and .phar uploads, and restrict access (IP allowlist) to the site or affected endpoints while you test.

Q: Does setting phar.readonly = 1 protect me?
A: phar.readonly helps but is not a silver bullet. It prevents creation/modification of PHAR archives on the server, but PHAR metadata deserialization can still occur when a PHAR file is read. Combined mitigations are required.

Q: Should I remove the plugin entirely?
A: If you do not need the plugin, remove it. If you need it, update to 3.2.5 and apply the suggested hardening.

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How WP-Firewall protects you (brief)

• Managed, performance-optimized WAF rules that block common exploit signatures including PHAR-based deserialization attempts.
• Malware scanning and alerting for suspicious files and changes.
• Virtual patching capability so your site can be protected while you perform necessary updates and tests.
• Monitoring and reporting so you can see exploit attempts and mitigation effectiveness in near real-time.

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Closing notes — prioritize patching, but don’t forget follow-up

This vulnerability is both high severity and easy to attempt because it requires no authentication. The fastest, safest route is to update to Redirection for Contact Form 7 version 3.2.5. If you cannot update immediately, layer your defenses: virtual patching via a WAF, server-level rules to block phar:// et .phar files, file upload hardening, and active monitoring for indicators of exploitation.

If you need support, incident response, or help configuring protections and monitoring for multiple WordPress sites, our WP-Firewall team is available to assist — our managed tools are designed to deliver emergency virtual patching, contextual WAF rules, and remediation guidance for critical plugin vulnerabilities like this one.

Stay safe, and act now — the window between disclosure and automated exploitation is short.