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Formidable Form Builder <= 4.09.04 — Unauthenticated Stored Cross-Site Scripting

CVE-2021-24884Published · Updated

Action summary

Affected: <4.09.05Update to 4.09.05 or newer

All remediation steps
Watch plugin
Severity
Critical9.6
CVSS
9.6
CVSS 3.1 · CNA (Wordfence)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
What does this vector mean?
AV:N Attack vector
Network
AC:L Attack complexity
Low
PR:N Privileges required
None
UI:R User interaction
Required
S:C Scope
Changed
C:H Confidentiality
High
I:H Integrity
High
A:H Availability
High
Weakness
CWE-79 Cross-Site Scripting
Required access
No account needed
Exploit prediction (EPSS)
No score
CISA KEV
Not listed
On this page8

Am I affected?

Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder formidable

  1. Affected< 4.09.05
  2. Patched in4.09.05

Update to 4.09.05 or newer.

You are affected if you run < 4.09.05. Version 4.09.05 and later are not affected by this issue.

  • Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder.
  • No admin access? Run a passive check of your site. It reads public files only.
  • No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

  1. Update to version 4.09.05, or a newer patched version
  2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
  3. Watch Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence, credited to Maximilian Barz.

The Formidable Form Builder WordPress plugin before 4.09.05 allows to inject certain HTML Tags like <audio>,<video>,<img>,<a> and<button>.This could allow an unauthenticated, remote attacker to exploit a HTML-injection byinjecting a malicous link. The HTML-injection may trick authenticated users to follow the link. If the Link gets clicked, Javascript code can be executed. The vulnerability is due to insufficient sanitization of the "data-frmverify" tag for links in the web-based entry inspection page of affected systems. A successful exploitation incomibantion with CSRF could allow the attacker to perform arbitrary actions on an affected system with the privileges of the user. These actions include stealing the users account by changing their password or allowing attackers to submit their own code through an authenticated user resulting in Remote Code Execution. If an authenticated user who is able to edit Wordpress PHP Code in any kind, clicks the malicious link, PHP code can be edited.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

More in Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder

All 29
More vulnerabilities in Formidable Forms – Contact Form, Survey, Quiz, Payment, Calculator Form & Custom Form Builder
SeverityVulnerabilityCVEPublished
High8.8Authenticated (Subscriber+) Arbitrary Plugin Installation via 'file_url' Parameter
≤6.35Update to 7.0
CVE-2026-89435
High7.5Unauthenticated Denial of Service
<7.0Update to 7.0
CVE-2026-85642
Medium5.3Unauthenticated Content Injection
≤6.34Update to 6.35
CVE-2026-85641
Medium6.5Unauthenticated Arbitrary Shortcode Execution
≤6.34Update to 6.35
CVE-2026-19857
High7.2Unauthenticated Stored Cross-Site Scripting via 'frm_user_id' Parameter
≤6.33.1Update to 6.34
CVE-2026-18331

Same weakness (Cross-Site Scripting)

All Cross-Site Scripting
Other Cross-Site Scripting vulnerabilities
SeverityVulnerabilityCVEPublished
High7.2Unauthenticated Stored Cross-Site Scripting via Comment User-Agent Header
EZ SQL Reports Shortcode Widget and DB Backup≤5.25.25Update to 5.26.45
CVE-2026-120688
Critical9.8Unauthenticated Arbitrary File Upload via File Upload via Public Form Submission
Chatterbug Forms – Fast, Flexible WordPress Form Builder≤1.0.2Update to 1.1
CVE-2026-125055
Critical9.8Unauthenticated PHP Object Injection to Remote Code Execution via 'form' Parameter
ELEX WordPress HelpDesk & Customer Ticketing System≤3.3.9Update to 3.4.0
CVE-2026-119077
Medium5.3Unauthenticated Sensitive Information Exposure in 'search' Parameter
Customer Reviews for WooCommerce≤5.127.0Update to 5.128.0
CVE-2026-121518

Timeline

  1. CVE published

    Severity critical, CVSS 9.6

  2. Record last updated

Sources & licenses

Wordfence record
Vulnerability data
Wordfence Intelligence. Copyright 2012-2026 Defiant Inc. Licensed under the CC BY-SA 4.0.
CVE® identifiers
Copyright 1999-2026 The MITRE Corporation. Used under the CVE Program. CVE® is a registered trademark of The MITRE Corporation.
CVSS / CWE
National Vulnerability Database (NVD), shown unmodified. This product uses the NVD API but is not endorsed or certified by the NVD.
VulnCrest content
Summary, remediation guidance and page layout © VulnCrest. Not sourced from NVD.

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