CVE-2026-109515 MailOptin <= 1.2.78.6 - Unauthenticated Privilege Escalation to 'form_custom_field_mappings' Parameter
Unauthenticated attackers can take over any WordPress account, including administrators, by manipulating user registration parameters in the MailOptin plugin.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-109515?
CVE-2026-109515 is a critical vulnerability in properfraction MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc., published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-269
Which versions are affected by CVE-2026-109515?
How do I fix CVE-2026-109515?
No fix has been published for CVE-2026-109515 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-109515 being exploited?
There is no known exploitation of CVE-2026-109515 in the wild and no public exploit code.
Sources
Also known as GHSA-f6hj-w62g-r97p.