---
id: CVE-2026-75957
title: >-
  The Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin for
  WordPress is vulnerable to Authentication Bypass in all versions up to, and
  including, 2.15.0 via the `checkout_form` parameter of the
  `login_customer_after_che…
summary: >-
  The Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin for
  WordPress is vulnerable to Authentication Bypass in all versions up to, and
  including, 2.15.0 via the `checkout_form` parameter of the
  `login_customer_after_che…
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'
cwe:
  - CWE-287
vendor: superdav42
product: Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform
affected:
  - ultimate_multisite_wordpress_multisite_saas_waas_platform <= 2.15.0
published: '2026-10-01'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T08:16:52.763'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75957'
references:
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L1223
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L208
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2489
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/checkout/class-checkout.php#L2700
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.14.2/inc/models/class-checkout-form.php#L1352
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L1223
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L208
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2489
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/checkout/class-checkout.php#L2700
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/browser/ultimate-multisite/tags/2.15.0/inc/models/class-checkout-form.php#L1352
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/changeset/3653622/ultimate-multisite/trunk/inc/checkout/class-checkout.php
    label: security@wordfence.com
  - url: >-
      https://plugins.trac.wordpress.org/changeset?reponame=&new=3653623%40ultimate-multisite%2Ftags%2F2.15.1&old=3634394%40ultimate-multisite%2Ftags%2F2.15.0
    label: security@wordfence.com
  - url: >-
      https://www.wordfence.com/threat-intel/vulnerabilities/id/66cb8c6f-d405-4115-a626-040e9b5b1e62?source=cve
    label: security@wordfence.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-01T08:40:11.740Z'
---

## Overview

The Ultimate Multisite – WordPress Multisite SaaS & WaaS Platform plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 2.15.0 via the `checkout_form` parameter of the `login_customer_after_checkout` function. This is due to the publicly accessible `wu_ajax_nopriv_wu_validate_form` AJAX handler accepting a freely obtainable checkout nonce, and the `checkout_form=wu-finish-checkout` parameter causing `get_validation_rules()` to discard all validation rules while `finish_checkout_form_fields()` returns an empty step list — forcing `is_last_step()` to return true and routing the request directly into full order processing — after which `maybe_create_customer()` resolves the attacker-supplied `email_address` to an existing WordPress user ID without any authentication or ownership verification, and `login_customer_after_checkout()` calls `wp_set_auth_cookie()` for that user ID via a passwordless code path. This makes it possible for unauthenticated attackers to log in as any existing WordPress user — including a Network Super Admin — simply by knowing their email address. Exploitation requires that the targeted user account has no pre-existing Ultimate Multisite customer record; accounts such as a Network Super Admin on a fresh Multisite install, or any administrator or editor added before Ultimate Multisite was configured, satisfy this condition and are therefore exploitable.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.