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CVE-2026-18331— Formidable Forms <= 6.33.1 - Unauthenticated Stored Cross-Site Scripting via 'frm_user_id' Parameter

Quick assessment

Affected
strategy11team Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More
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 Formidable Forms是WordPress基金会开源的一款表单创建插件。 WordPress Formidable Forms 6.33.1及之前版本存在跨站脚本漏洞，该漏洞源于对'frm_user_id'参数的输入清理和输出转义不足，可能导致未经身份验证的攻击者注入任意Web脚本，在用户访问页面时执行。

CVSS 7.2 · High EPSS 0.49% · P42

Possible ATT&CK Techniques 1 AI

T1059.001 · PowerShell

Affected Version Matrix 1

VendorProduct Version RangeStatus
strategy11team Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More ≤ 6.33.1 affected
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I. Basic Information for CVE-2026-18331

Vulnerability Information
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Vulnerability Title
Formidable Forms <= 6.33.1 - Unauthenticated Stored Cross-Site Scripting via 'frm_user_id' Parameter
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
WordPress Formidable Forms 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
WordPress Formidable Forms是WordPress基金会开源的一款表单创建插件。 WordPress Formidable Forms 6.33.1及之前版本存在跨站脚本漏洞，该漏洞源于对'frm_user_id'参数的输入清理和输出转义不足，可能导致未经身份验证的攻击者注入任意Web脚本，在用户访问页面时执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
strategy11team Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More 0 ~ 6.33.1 -

II. Public POCs for CVE-2026-18331

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III. Intelligence Information for CVE-2026-18331

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News Coverage for CVE-2026-18331 (1)

Vendor Pages for CVE-2026-18331 (1)

Other References for CVE-2026-18331 (1)

IV. Related Vulnerabilities

Same vendor: strategy11team
Same weakness: CWE-79