CVE-2026-18331Formidable Forms <= 6.33.1 - Unauthenticated Stored Cross-Site Scripting via 'frm_user_id' Parameter
Updated under an hour ago ()
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It affects strategy11team Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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.
- CVSS
- 7.2 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- Weakness (CWE)
- CWE-79
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Wordfence
- NVD analysis
- Deferred
- Record last updated
- Aug 26, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
strategy11team Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More strategy11team:formidable_forms_wordpress_form_builder_for_contact_forms_calculators_quizzes_and_more (from the name) | through 6.33.1 | CNA record |
References
- https://www.wordfence.com/threat-intel/vulnerabilities/id/f03b09ad-257c-48c9-8ecc-36f60f178f80?source=cve
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/models/fields/FrmFieldType.php#L1830
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/models/fields/FrmFieldType.php#L2083
- https://plugins.trac.wordpress.org/browser/formidable/trunk/js/formidable_admin.js#L1
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/models/FrmEntry.php#L982
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/models/FrmEntry.php#L819
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/models/FrmEntry.php#L846
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/controllers/FrmEntriesController.php#L752
- https://plugins.trac.wordpress.org/browser/formidable/trunk/classes/controllers/FrmHooksController.php#L69
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.