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CVE-2021-24884 is a vulnerability in the Formidable Form Builder WordPress plugin prior to version 4.09.05, where insufficient sanitization of the "data-frmverify" attribute allows unauthenticated attackers to inject HTML tags such as <audio>, <video>, <img>, <a>, and <button> into the web-based entry inspection page. This enables HTML injection attacks, potentially tricking authenticated users into clicking malicious links, which can lead to JavaScript execution (XSS) and further exploitation.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository provides a working exploit for CVE-2021-24884, a stored XSS vulnerability in the Formidable Forms WordPress plugin (version 4.09.04). The exploit leverages the ability to inject HTML tags (such as <img>, <a>, <button>) into form entries, which are then rendered in the admin interface. The attacker crafts a payload that, when viewed by an authenticated admin user, executes JavaScript to extract a WordPress nonce from the theme editor page. Using this nonce, the script performs a CSRF attack to POST a PHP webshell into the theme's index.php file via the theme editor, resulting in remote code execution (RCE) on the server. The exploit includes a callback to an attacker-controlled server to confirm success. The repository contains two files: a detailed README.md with background, references, and the full payload, and XSS_PAYLOAD_FORMIDABLE.txt, which contains the actual exploit code and encoded payload. The exploit requires social engineering to trick an authenticated user with code editing privileges into clicking a malicious link. The main attack vectors are browser-based (XSS/CSRF) and network-based (HTTP requests to the WordPress admin interface).
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