CVE-2026-103540 in Form Tools
Summary
by MITRE • 10/01/2026
A security vulnerability has been detected in formtools.org Form Tools up to 3.1.1. This vulnerability affects the function Clients::updateClientSettingsTab of the file global/code/Clients.class.php of the component Client Settings. The manipulation of the argument page_titles leads to improper neutralization of special elements used in a template engine. It is possible to initiate the attack remotely. The exploit has been disclosed publicly and may be used. The project was informed of the problem early through an issue report but has not responded yet.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified within Form Tools versions up to 3.1.1 represents a significant security risk stemming from improper input validation in the client settings management module. Specifically, the flaw resides in the Clients::updateClientSettingsTab function located in the global/code/Clients.class.php file. This component is responsible for handling updates to client configuration data, particularly when administrators modify interface elements such as page titles. The core technical deficiency lies in how the application processes the page_titles argument before passing it into a template engine. Instead of properly neutralizing special characters or escaping them according to safe coding practices, the system allows raw input to be interpreted directly by the rendering layer. This failure to sanitize user-supplied data creates an environment where malicious scripts can be injected and subsequently executed within the context of the victim's browser session when the affected page is viewed.
This specific technical flaw aligns with Common Weakness Enumeration CWE-79, which classifies Improper Neutralization of Input During Web Page Generation known as Cross-site Scripting (XSS). The vulnerability enables a Remote Code Execution scenario in the form of stored or reflected XSS depending on how the data persists within the application's database and retrieval mechanisms. Because the manipulation occurs during an administrative update action, if the malicious payload is saved to the database, it becomes persistent across sessions for any user who accesses that specific client configuration view. This transforms a simple input validation error into a potent vector for session hijacking, credential theft, or defacement of the application interface. The ability to initiate this attack remotely means that an authenticated attacker with access to the client settings module can exploit this flaw without requiring physical proximity or local system access, significantly expanding the attack surface available to adversaries who have compromised legitimate user credentials.
The operational impact of this vulnerability is severe for organizations relying on Form Tools for customer relationship management and data organization. Successful exploitation allows attackers to execute arbitrary JavaScript code in the context of the web application. This can lead to the theft of sensitive administrative cookies, facilitating unauthorized access to other parts of the system or impersonation of legitimate users. Furthermore, it enables phishing attacks where victims are redirected to malicious sites designed to harvest additional credentials. Given that Form Tools is often used by businesses to manage client data, the breach of integrity and confidentiality can have downstream effects on business operations and customer trust. The fact that exploit code has been disclosed publicly increases the likelihood of automated scanning tools targeting this specific weakness in unpatched instances, making immediate remediation critical for deployed environments.
Industry frameworks such as MITRE ATT&CK categorize this type of vulnerability under techniques related to Client-side Scripting Injection, specifically T1059. The lack of response from the project maintainers despite early notification highlights a gap in vendor security support that users must account for in their risk management strategies. In the absence of an official patch or update from formtools.org, organizations should implement compensating controls to mitigate the risk. These measures include deploying Web Application Firewalls configured with rulesets capable of detecting and blocking XSS payloads within POST requests targeting the Clients.class.php endpoint. Additionally, strict Content Security Policy headers can be implemented to restrict script execution sources, thereby neutralizing the impact even if an injection attempt succeeds. Regular security audits and input validation checks on all administrative interfaces are essential practices to prevent similar vulnerabilities from being introduced or exploited in custom modifications of the software.