CVE-2021-24896 in Caldera Forms Plugin
Summary
by MITRE • 12/13/2021
The Caldera Forms WordPress plugin before 1.9.5 does not sanitise and escape the Form Name before outputting it in attributes, which could allow high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.
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Analysis
by VulDB Data Team • 12/16/2021
The vulnerability identified as CVE-2021-24896 affects the Caldera Forms WordPress plugin version 1.9.4 and earlier, representing a critical cross-site scripting flaw that undermines the security posture of WordPress installations. This vulnerability specifically targets the plugin's handling of form names within HTML attributes, creating a pathway for malicious actors to inject harmful scripts. The issue manifests when high-privilege users manipulate form names containing malicious code, which then gets rendered without proper sanitization in the plugin's user interface or generated HTML output.
The technical flaw stems from inadequate input validation and output escaping mechanisms within the Caldera Forms plugin codebase. When administrators or users with sufficient privileges create or modify forms, the plugin fails to properly sanitize the form name parameter before incorporating it into HTML attributes such as id, class, or data attributes. This omission creates a classic XSS vulnerability where malicious scripts embedded within form names can execute in the context of other users' browsers. The vulnerability is particularly concerning because it exploits the trust placed in high-privilege users, who typically have elevated capabilities including the ability to create forms with potentially dangerous content.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to escalate privileges, steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious websites. Even though the plugin's design may restrict unfiltered_html capability for most users, the vulnerability allows high-privilege users to bypass these protections through the form name field. This creates a scenario where administrators or editors with form creation privileges can inadvertently introduce malicious code that persists and executes whenever the affected forms are displayed or manipulated within the WordPress admin interface.
Security professionals should note that this vulnerability aligns with CWE-79, which categorizes cross-site scripting flaws as one of the most prevalent and dangerous web application vulnerabilities. The attack vector follows patterns consistent with ATT&CK technique T1566.001, where adversaries leverage web application vulnerabilities to execute malicious code in user browsers. The vulnerability also demonstrates characteristics of privilege escalation through compromised administrative accounts, as described in ATT&CK technique T1078.101, where attackers exploit legitimate credentials to gain elevated access within the application environment.
Mitigation strategies should prioritize immediate plugin updates to version 1.9.5 or later, which contain the necessary sanitization fixes. Additionally, administrators should implement strict input validation policies for form name fields and consider implementing content security policies to limit the execution scope of any potential XSS payloads. Regular security audits of plugin configurations and user privilege assignments should be conducted to prevent unauthorized form modifications. Organizations should also consider implementing web application firewalls and monitoring for suspicious form creation patterns to detect potential exploitation attempts before they succeed. The vulnerability serves as a reminder of the critical importance of proper input sanitization and output escaping in web applications, particularly within content management systems where user-generated content can be leveraged for malicious purposes.