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CVE-2026-18331

HIGH 7.2 CVSS 3.1
Published
August 26, 2026
Last modified
August 26, 2026
NVD status
Deferred
Reported by
security@wordfence.com
Weakness
CWE-79
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Description

The Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'frm_user_id' parameter in all versions up to, and including, 6.33.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. By forging frm_user_id to match an administrator's user ID — discoverable via the public WordPress REST API — an unauthenticated attacker causes wp_kses_post() to serve as the only output filter, which preserves the injected payload structurally intact; the plugin's admin JavaScript then decodes and executes it automatically on page load.

Affected WordPress components

  • Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More Plugin · formidable
    Confirmed match Active
    Up to and including 6.33.1
    View on WordPress.org

A confirmed match is backed by the plugin or theme slug. A possible match is based on the product name only and should be verified.

Affected products and versions

  • strategy11team Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More — Up to and including 6.33.1

References