CVE-2026-118500 in Cool FormKit Lite Plugin
Summary
by MITRE • 10/30/2026
The Cool FormKit Lite – Advanced Form Builder for Elementor plugin for WordPress is vulnerable to Stored DOM-Based Cross-Site Scripting via the '_elementor_data.form_fields[].custom_id' parameter in all versions up to, and including, 2.7.9 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The esc_html() call applied at server emission is bypassed because the HTML fragment-serialization algorithm restores " to a raw double-quote inside text nodes when jQuery .html() extracts the template, allowing the attacker-controlled custom_id to break out of an HTML attribute context within the plugin's own frontend script.
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Analysis
by VulDB Data Team • 10/30/2026
The Cool FormKit Lite – Advanced Form Builder for Elementor WordPress plugin contains a critical security vulnerability affecting all versions up to and including 2.7.9. This flaw is classified as a Stored DOM-Based Cross-Site Scripting (XSS) issue, which represents a significant risk to the integrity of websites utilizing this form builder tool. The vulnerability stems from insufficient input sanitization and output escaping mechanisms within the plugin's codebase, specifically targeting the _elementor_data.form_fields[].custom_id parameter. This architectural weakness allows malicious actors with authenticated access at contributor level or higher to inject arbitrary web scripts into stored data structures that are subsequently rendered in user-facing pages.
The technical mechanism of this exploitation is particularly sophisticated due to its reliance on client-side DOM manipulation rather than traditional server-side rendering flaws. When an attacker submits a crafted payload via the custom_id parameter, it is stored within the plugin's configuration data without adequate validation or encoding. The vulnerability manifests when the frontend JavaScript code attempts to render these form fields using jQuery .html() method. Although the server emits HTML fragments that appear sanitized through the use of esc_html(), this protection is effectively bypassed during the client-side processing phase. Specifically, the HTML fragment-serialization algorithm used by browsers restores escaped entities such as " back into raw double-quote characters when they are inside text nodes. This behavior allows the attacker-controlled custom_id value to break out of its intended HTML attribute context and execute arbitrary JavaScript code within the victim's browser session.
The operational impact of this vulnerability is severe, particularly because it requires only contributor-level access rather than administrator privileges. In many WordPress environments, contributors have significant capabilities including creating posts and managing certain content types, making them a more accessible target for attackers who may compromise lower-privileged accounts through phishing or credential theft. Once the malicious script is injected, it executes whenever any user accesses pages containing the compromised form fields. This can lead to session hijacking, where an attacker steals administrative cookies to gain full control over the WordPress installation. It also enables defacement of website content, redirection of users to malicious sites for further exploitation such as malware distribution or phishing attacks, and potential data exfiltration from forms processed by the plugin.
From a classification perspective, this vulnerability aligns with CWE-79, which covers Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. More specifically, it falls under CWE-80 due to its DOM-based nature where client-side scripts process untrusted data without proper validation. In the context of the MITRE ATT&CK framework for enterprise security, this vulnerability facilitates techniques associated with T1059 Command and Control scripting interpretation, allowing attackers to execute arbitrary commands within the victim's browser environment. It also supports lateral movement if session tokens are stolen, potentially leading to privilege escalation from contributor to administrator levels through subsequent exploitation of other vulnerabilities or social engineering tactics leveraging the compromised account.
Mitigation strategies must address both immediate remediation and long-term security posture improvements. The most effective solution is to upgrade the Cool FormKit Lite plugin to version 2.7.10 or later, where developers have implemented proper input sanitization using WordPress functions like sanitize_text_field() for custom_id values and ensured consistent output escaping that accounts for DOM-based contexts. For organizations unable to update immediately due to compatibility constraints, implementing a Web Application Firewall with rules specifically targeting XSS payloads in form field parameters can provide temporary protection. Additionally, enforcing strict Content Security Policy headers can mitigate the impact by restricting script execution sources and preventing inline scripts from running unless explicitly whitelisted.
Security teams should also review access controls within their WordPress installations to ensure that contributor-level accounts are granted only the minimum necessary permissions required for their roles. Implementing multi-factor authentication for all administrative and editor accounts reduces the likelihood of initial compromise through credential theft. Regular security audits focusing on third-party plugin code quality and adherence to OWASP guidelines can help identify similar vulnerabilities before they are exploited in production environments. Developers working with WordPress plugins must be aware that server-side escaping alone is insufficient when client-side JavaScript manipulates DOM elements, requiring a defense-in-depth approach that includes both server-side validation and safe client-side rendering practices using methods like textContent instead of innerHTML where possible to prevent such bypasses.