CVE-2021-24884: 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 a...

Description

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.

Metrics

CVSS 3.1

9.6/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

EPSS Probability

3.08%

86.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Strategy11	Formidable Form Builder	< 4.09.05

References

https://github.com/S1lkys/XSS-in-Formidable-4.09.04/blob/main/XSS-in-Formidable-4.09.04.pdfExploit, Third Party Advisory
https://github.com/Strategy11/formidable-forms/pull/335/filesPatch, Third Party Advisory
https://wpscan.com/vulnerability/b57dacdd-43c2-48f8-ac1e-eb8306b22533Exploit, Third Party Advisory
https://github.com/S1lkys/XSS-in-Formidable-4.09.04/blob/main/XSS-in-Formidable-4.09.04.pdfExploit, Third Party Advisory
https://github.com/Strategy11/formidable-forms/pull/335/filesPatch, Third Party Advisory
https://wpscan.com/vulnerability/b57dacdd-43c2-48f8-ac1e-eb8306b22533Exploit, Third Party Advisory

Timeline

Published: Oct 25, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-24884?

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.

How severe is CVE-2021-24884?

CVE-2021-24884 has a CVSS score of 9.6/10 (CRITICAL severity). The EPSS model estimates a 3.08% probability of exploitation in the next 30 days.

How do I fix CVE-2021-24884?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.