{"id":"CVE-2026-109515","title":"MailOptin <= 1.2.78.6 - Unauthenticated Privilege Escalation to 'form_custom_field_mappings' Parameter","summary":"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_l…","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-269"],"vendor":"properfraction","product":"MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.","affected":["mailoptin_popup_optin_forms_email_newsletters_for_mailchimp_hubspot_aweber_etc. <= 1.2.78.6"],"published":"2026-10-16","updated":"2026-10-16","sourceUpdated":"2026-10-16T04:27:01.480Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-109515","references":[{"url":"https://www.wordfence.com/threat-intel/vulnerabilities/id/96111116-6b6f-42fc-98d8-6f5c27dc3c1c?source=cve"},{"url":"https://plugins.trac.wordpress.org/browser/mailoptin/tags/1.2.78.5/src/connections/WordPressUserRegistrationConnect/Subscription.php#L68"},{"url":"https://plugins.trac.wordpress.org/browser/mailoptin/tags/1.2.78.5/src/core/src/Connections/AbstractConnect.php#L84"},{"url":"https://plugins.trac.wordpress.org/browser/mailoptin/tags/1.2.78.5/src/core/src/AjaxHandler.php#L699"},{"url":"https://plugins.trac.wordpress.org/changeset?reponame=&new=3744644%40mailoptin%2Ftrunk&old=3738326%40mailoptin%2Ftrunk#file4"},{"url":"https://plugins.trac.wordpress.org/changeset/3744644/mailoptin/trunk/src/connections/WordPressUserRegistrationConnect/Subscription.php"}],"tags":["cve.org"],"ingestedAt":"2026-10-16T04:58:47.491Z","slug":"CVE-2026-109515","body":"## Overview\n\nThe 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.\n\n## Affected\n\n- `mailoptin_popup_optin_forms_email_newsletters_for_mailchimp_hubspot_aweber_etc. <= 1.2.78.6`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}