Formidable Form Builder < 2.05.03 - Reflected Cross-Site Scripting

2017-11-13 00:00
Jouko Pynnöne

Strategic Overview

Status
Patched in 2.05.03
Affected Plugin
Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More
Affected Version
< 2.05.03
CVSS
6.1Medium
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE pending
View all Formidable Forms – WordPress Form Builder for Contact Forms, Calculators, Quizzes & More vulnerabilities

At a glance

This record tracks a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Formidable Forms WordPress plugin, affecting versions < 2.05.03. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 2.05.03; sites on affected versions should update now. Disclosed November 2017, reported by Jouko Pynnöne.

Vulnerability Overview

The Formidable Form Builder plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'before_html' parameter passed through the frm_forms_preview AJAX action in versions before 2.05.03 due to insufficient input sanitization and output escaping. This makes it possible for attackers to inject arbitrary web scripts that execute in a victim's browser whenever they successfully trick a victim into performing an action like clicking on a link.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Formidable Forms < 2.05.03 carries this weakness at before_html, and reaching it takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Formidable Forms the fix is 2.05.03: builds < 2.05.03 are affected, anything from 2.05.03 onward is not.

Remediation

Update to version 2.05.03, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Formidable Forms: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Formidable Forms 2.05.03 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Alerts

External References

https://www.wordfence.com/threat-intel/vulnerabilities/id/c0e6f20a-3a5c-4782-9852-9891b93d765f

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