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Ultimate Multisite vulnerabilities
Ultimate Multisite has 1 known vulnerability in this database. The most recent published record is dated 1 Oct 2026.
- Known vulnerabilities
- 1
- Active installs
- 70+
- Latest version
- 2.16.1
- Last updated
- 12 Sep 2026
- Most recent
- 1 Oct 2026
Find it in your WordPress dashboard under Plugins. Severity is based on the CVSS score published with the CVE where one is available.
| Vulnerability | Severity | Affected | Fix | Published |
|---|---|---|---|---|
| Authentication bypass CVE-2026-75957 | Critical 9.8 | Up to 2.15.0 | Fixed in a later version (latest 2.16.1) | 6 d ago |
Read the published descriptions
- CVE-2026-75957, 1 Oct 2026
- 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. CVE record
What to do if you run Ultimate Multisite
If you run Ultimate Multisite, open WordPress and check the installed version in Plugins. Compare it with the affected versions in the vulnerability record. If a fixed version is available, take a current backup and update to that version or the latest supported release.
If no fixed version exists, consider disabling and removing the plugin or replacing it with a maintained alternative. After dealing with the affected software, check administrator users, unexpected file changes, redirects, unfamiliar pages and security logs for signs that the site may already have been altered.
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