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MailOptin <= 1.2.78.6 — Unauthenticated Privilege Escalation to 'form_custom_field_mappings' Parameter

CVE-2026-109515Published · Updated

Action summary

Affected: ≤1.2.78.6Update to 1.2.78.7 or newer

All remediation steps
Watch plugin
Severity
Critical9.8
CVSS
9.8
CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
What does this vector mean?
AV:N Attack vector
Network
AC:L Attack complexity
Low
PR:N Privileges required
None
UI:N User interaction
None
S:U Scope
Unchanged
C:H Confidentiality
High
I:H Integrity
High
A:H Availability
High
Weakness
CWE-269 Privilege Escalation
Required access
No account needed
Exploit prediction (EPSS)
0.4% chance in 30 days38th percentile
CISA KEV
Not listed
On this page8

Am I affected?

MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. mailoptin

  1. Affected≤ 1.2.78.6
  2. Patched in1.2.78.7

Update to 1.2.78.7 or newer.

You are affected if you run ≤ 1.2.78.6. Version 1.2.78.7 and later are not affected by this issue.

  • Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc..
  • No admin access? Run a passive check of your site. It reads public files only.
  • No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

  1. Update to version 1.2.78.7, or a newer patched version
  2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
  3. Watch MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence, credited to Kuba.

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.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

More in MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.

All 8
More vulnerabilities in MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.
SeverityVulnerabilityCVEPublished
Medium6.4Authenticated (Contributor+) Stored Cross-Site Scripting
≤1.2.78.0Update to 1.2.78.1
CVE-2026-66703
Critical9.8Unauthenticated Privilege Escalation
≤1.2.77.3Update to 1.2.78.0
CVE-2026-57813
Medium4.4Authenticated (Administrator+) Stored Cross-Site Scripting
≤1.2.75.0Update to 1.2.75.1
CVE-2025-58596
Medium5.4Authenticated (Contributor+) Stored Cross-Site Scripting
≤1.2.70.3Update to 1.2.70.4
CVE-2024-8628
Medium5.5Authenticated (Admin+) Cross Site Scripting
1.2.54.0 – 1.2.54.0Update to 1.2.54.1
CVE-2023-23980

Same weakness (Privilege Escalation)

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CVE-2026-120688
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CVE-2026-125055
Critical9.8Unauthenticated PHP Object Injection to Remote Code Execution via 'form' Parameter
ELEX WordPress HelpDesk & Customer Ticketing System≤3.3.9Update to 3.4.0
CVE-2026-119077
Medium5.3Unauthenticated Sensitive Information Exposure in 'search' Parameter
Customer Reviews for WooCommerce≤5.127.0Update to 5.128.0
CVE-2026-121518

Timeline

  1. CVE published

    Severity critical, CVSS 9.8

  2. Record last updated

Sources & licenses

Wordfence record
Vulnerability data
Wordfence Intelligence. Copyright 2012-2026 Defiant Inc. Licensed under the CC BY-SA 4.0.
CVE® identifiers
Copyright 1999-2026 The MITRE Corporation. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
CVSS / CWE
National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
EPSS
Exploit Prediction Scoring System by FIRST.org.
VulnCrest content
Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.

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