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CVE-2026-89435— Formidable Forms <= 6.35 - Authenticated (Subscriber+) Arbitrary Plugin Installation via 'file_url' Parameter

Quick assessment

Affected
strategy11team Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder
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 插件"Formidable Forms – WordPress 表单构建器（用于联系表单、计算器、测验等）”在所有 6.35 及以下版本中，存在通过 参数导致的任意插件安装漏洞。该漏洞源于 函数中对 URL 前缀的验证不足，以及权限回调机制仅依赖一个可被任何拥有 可委托能力的用户获取的共享令牌，而未检查 或 能力。这使得拥有订阅者（Subscriber）及以上权限的已认证攻击者能够在服务器上安装任意插件。此外，利用该漏洞还要求目标站点仅使用免费版（即未安装 Formidable Pro）。

CVSS 8.8 · High
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I. Basic Information for CVE-2026-89435

Vulnerability Information
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Vulnerability Title
Formidable Forms <= 6.35 - Authenticated (Subscriber+) Arbitrary Plugin Installation via 'file_url' 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 Arbitrary Plugin Installation in all versions up to, and including, 6.35 via the 'file_url' parameter parameter. This is due to insufficient URL prefix validation in validate_url_is_in_s3_bucket() and a permission callback that relies solely on a shared token obtainable by any user with the delegable frm_view_forms capability, without checking install_plugins or activate_plugins capabilities. This makes it possible for authenticated attackers, with subscriber-level access and above, to install arbitrary plugins on the server. Exploitation additionally requires that the site is free-only (Formidable Pro is NOT installed).
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
输出中的特殊元素转义处理不恰当(注入)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
strategy11team Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder 0 ~ 6.35 -

II. Public POCs for CVE-2026-89435

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III. Intelligence Information for CVE-2026-89435

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Other References for CVE-2026-89435 (8)

IV. Related Vulnerabilities

Same vendor: strategy11team
Same weakness: CWE-74