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CVE-2026-109515— MailOptin <= 1.2.78.6 - Unauthenticated Privilege Escalation to 'form_custom_field_mappings' Parameter

Quick assessment

Affected
properfraction MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

WordPress 插件 "MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber 等”在 1.2.78.6 及以下的所有版本中存在权限提升漏洞。该漏洞源于 端点在处理攻击者提供的 参数时，未对目标键实施白名单验证。这导致攻击者可控制字段映射，从而覆盖管理员保存的映射配置，并将任意 表字段名（包括 和 ）直接传入 函数（通过 函数调用）。 利用此漏洞，未认证的攻击者可通过提供目标用户的数字 ，强制 以更新（U

CVSS 9.8 · Critical EPSS 0.44% · P37

Possible ATT&CK Techniques 2 AI

T1551.001 T1133 · External Remote Services

Affected Version Matrix 1

VendorProduct Version RangeStatus
properfraction MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. ≤ 1.2.78.6 affected
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I. Basic Information for CVE-2026-109515

Vulnerability Information
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Vulnerability Title
MailOptin <= 1.2.78.6 - Unauthenticated Privilege Escalation to 'form_custom_field_mappings' Parameter
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
特权管理不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
properfraction MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc. 0 ~ 1.2.78.6 -

II. Public POCs for CVE-2026-109515

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III. Intelligence Information for CVE-2026-109515

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Vendor Pages for CVE-2026-109515 (3)

IV. Related Vulnerabilities

Same product: MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber Etc.
Same vendor: properfraction
Same weakness: CWE-269

V. Comments for CVE-2026-109515

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