CVE-2021-24884: Formidable Form Builder: Allows to inject certain HTML Tags like <audio>

Formidable Form Builder: Allows to inject certain HTML Tags like <audio>

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.

Description from the National Vulnerability Database, published by WPScan

What it means for a small business

Formidable Form Builder is a WordPress plugin. If your website uses it, the flaw is on your site whether or not anyone has noticed yet: attackers scan the whole internet for the plugins with published flaws, usually within days of a record like this one going public.

Most small-business sites run 15 to 40 plugins, and few owners know the list. You can check from WordPress itself (Plugins, then Installed Plugins), or let our free plugin check look it up by name.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 3.1%, higher than 87% of CVEs. That’s above average: worth scheduling this week. Scored October 29, 2026, updated daily.

Check your own setup

Is Formidable Form Builder safe? Every recorded flaw in it, the version that fixes each, and whether it’s still maintained.
Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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