CVE-2026-109515 — The MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.¶
Key facts
CVE-2026-109515 is a Critical (9.8) vulnerability: The MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-109515 |
| Severity | Critical (9.8) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-109515/ |
Details¶
English | 한국어
Description¶
The MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 1.2.78.6 This is due to the subscribe_to_email_list endpoint accepting an attacker-supplied optin_data[form_custom_field_mappings] parameter without any allow-list validation on destination keys, allowing the attacker-controlled mapping to override the administrator's saved mapping and pass arbitrary wp_users column names — including ID and user_pass — directly into wp_insert_user() via the subscribe() function. This makes it possible for unauthenticated attackers to force wp_insert_user() into UPDATE mode on any existing account by supplying a target user's numeric ID, overwrite that account's password with a pre-hashed value of their choosing, and thereby take over any WordPress user account — including administrators — leading to full site compromise. Exploitation requires that a WordPress User Registration opt-in form is published somewhere on the site, though the form's UUID is visible in page source and no authentication, nonce, or capability check is required to reach the vulnerable endpoint.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-109515 |
| Type | RCE |
| CVSS Score | 9.8 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-109515/poc.py
Usage¶
# Run PoC against target
python3 poc.py --target <TARGET_URL>
# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>
⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.
Test Lab¶
This repository includes a Docker-based test environment with both vulnerable and patched applications.
Quick Start¶
# Clone and navigate to CVE directory
cd CVE-2026-109515
# Start both applications
docker-compose up -d
# Run tests
./run-tests.sh # Linux/Mac
./run-tests.ps1 # Windows PowerShell
Application Endpoints¶
| Application | URL | Status |
|---|---|---|
| Vulnerable App | http://localhost:8080 | Shows vulnerability |
| Patched App | http://localhost:8081 | Demonstrates fix |
Directory Structure¶
├── README.md # English documentation
├── README_KO.md # Korean documentation
├── poc.py # PoC detection script
├── docker-compose.yml # Container orchestration
├── run-tests.sh # Linux/Mac test runner
├── run-tests.ps1 # Windows test runner
├── vulnerable-app/ # Vulnerable version
│ ├── app.py
│ ├── Dockerfile
│ └── requirements.txt
└── patched-app/ # Fixed version
├── app.py
├── Dockerfile
└── requirements.txt
References¶
- https://plugins.trac.wordpress.org/browser/mailoptin/tags/1.2.78.5/src/connections/WordPressUserRegistrationConnect/Subscription.php#L68
- https://plugins.trac.wordpress.org/browser/mailoptin/tags/1.2.78.5/src/core/src/AjaxHandler.php#L699
- https://plugins.trac.wordpress.org/browser/mailoptin/tags/1.2.78.5/src/core/src/Connections/AbstractConnect.php#L84
- https://plugins.trac.wordpress.org/changeset/3744644/mailoptin/trunk/src/connections/WordPressUserRegistrationConnect/Subscription.php
- https://plugins.trac.wordpress.org/changeset?reponame=&new=3744644%40mailoptin%2Ftrunk&old=3738326%40mailoptin%2Ftrunk#file4
- https://www.wordfence.com/threat-intel/vulnerabilities/id/96111116-6b6f-42fc-98d8-6f5c27dc3c1c?source=cve
Generated by PoC Generator on 2026-10-16T21:33:42.784351735
Frequently asked questions¶
What is CVE-2026-109515?¶
CVE-2026-109515 is a Critical (9.8) vulnerability: The MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-109515?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2026-109515?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
For authorized security testing and research only. See the full source and NVD record.