CVE-2026-109515
Received Received - Intake

Privilege Escalation in MailOptin WordPress Plugin

Publication date: 2026-10-16

Last updated on: 2026-10-16

Assigner: Wordfence

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.

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Meta Information

Published
2026-10-16
Last Modified
2026-10-16
Generated
2026-10-16
AI Q&A
2026-10-16
EPSS Evaluated
N/A
NVD
CVE-2026-109515
EUVD
EUVD-2026-102644

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
properfraction MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. 0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-269 The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

Attack-Flow Graph

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Executive Summary

This WordPress plugin vulnerability allows unauthenticated attackers to take over any user account, including administrators, by exploiting a flaw in the subscribe_to_email_list endpoint. The issue occurs because the plugin accepts attacker-controlled input that can override user registration mappings, letting attackers set arbitrary wp_users column values like ID and user_pass. This forces the system to update existing accounts with attacker-chosen passwords, leading to full site compromise.

Detection Guidance

Check if the MailOptin plugin version is up to 1.2.78.6 or lower. Look for unauthorized user account changes or password resets in WordPress logs. Inspect network traffic for requests to the subscribe_to_email_list endpoint with suspicious optin_data parameters.

Impact Analysis

If you use this plugin, attackers could hijack your WordPress admin account or any other user account on your site. They could then install malicious plugins, steal data, deface your site, or use it for further attacks. The attack requires only that a user registration form exists on your site, which is often visible in page source.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive user data, violating GDPR's data protection requirements and HIPAA's security rules for protected health information. A successful exploit may result in data breaches, unauthorized modifications, or loss of control over user accounts, all of which are compliance violations.

Mitigation Strategies

Update the MailOptin plugin to the latest version immediately. Disable any WordPress User Registration opt-in forms if not needed. Review user accounts for unauthorized changes and reset passwords for all admin accounts.

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