CVE-2021-24884

CRITICALNVD 9.69.6—
EchelonGraph scoreMEDIUM confidence

Score 9.6 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 9.6; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
9.6
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 3%CVSS: 9.6Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

The Formidable Form Builder WordPress plugin before 4.09.05 allows to inject certain HTML Tags like ,,, and.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.

CVSS v3
9.6
EG Score
9.6(medium)
EG Risk
64(Track*)
EG Risk 64/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity96% × 45%
Exploitation40% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS
86.3%
KEV
Not listed

Published

October 25, 2021

Last Modified

November 21, 2024

Advisory Details (3)

Auto-updated Jul 14, 2026
🔬 Proof of concept available. Patch available. Sources: github_pr.
generic🟡 PoC Available

Formidable Form Builder < 4.09.05 – Unauthenticated Stored Cross-Site Scripting | CVE 2021-24884 | Plugin Vulnerabilities

https://wpscan.com/vulnerability/b57dacdd-43c2-48f8-ac1e-eb8306b22533
github_pr Patch Available

Avoid XSS from data-verify / data-caution attributes

Patch available: Strategy11/formidable-forms v6.14.1 (PR #335 merged 2021-01-27)

https://github.com/Strategy11/formidable-forms/pull/335/files
generic

CVE-2021-24884/XSS-in-Formidable-4.09.04.pdf at main · S1lkys/CVE-2021-24884 · GitHub

https://github.com/S1lkys/XSS-in-Formidable-4.09.04/blob/main/XSS-in-Formidable-4.09.04.pdf

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 49× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 106 total refreshes for this CVE.

  1. 2026-07-24 14:15 UTCEPSS rescore
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Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCS1lkys/CVE-2021-24884
    First seen Oct 18, 2021

    If an authenticated user who is able to edit Wordpress PHP code in any kind, clicks a malicious link, PHP code can be edited through XSS in Formidable Forms 4.09.04.

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-24884?
CVE-2021-24884 is a critical vulnerability published on October 25, 2021. 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…
When was CVE-2021-24884 disclosed?
CVE-2021-24884 was first published in the National Vulnerability Database on October 25, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-24884 actively exploited?
CVE-2021-24884 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 86.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-24884?
CVE-2021-24884 has a CVSS v3 base score of 9.6 (NVD).
How do I remediate CVE-2021-24884?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-24884, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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