CVE-2026-84258 in click5 Plugin
Summary
by MITRE • 10/11/2026
The click5 CRM add-on to Ninja Forms WordPress plugin through 1.0.1 does not sanitise and escape content submitted through an unauthenticated endpoint before outputting it back in an admin page, leading to Stored XSS which could be used against high privilege users such as admin.
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Analysis
by VulDB Data Team • 10/11/2026
The vulnerability identified within the click5 CRM add-on for Ninja Forms WordPress plugin versions 1.0.1 and earlier represents a critical security flaw rooted in improper input validation and output encoding mechanisms. This specific issue manifests as a Stored Cross-Site Scripting (XSS) attack vector, which is particularly dangerous because it allows malicious scripts to persist on the target server rather than being executed solely within a victim's browser session during a single interaction. The core technical failure lies in the application's handling of data submitted through an unauthenticated endpoint. When users or attackers submit content via this interface, the system fails to properly sanitize the input, meaning it does not strip out potentially harmful script tags or event handlers before storage. Furthermore, when this stored data is subsequently rendered on administrative pages for review or management purposes, the application also fails to escape the output. This dual failure in both sanitization and escaping creates a direct pathway for arbitrary JavaScript execution within the context of the administrator's browser session.
From an operational perspective, the impact of this vulnerability is severe due to its unauthenticated nature combined with high-privilege target exposure. Because no authentication is required to trigger the initial injection point, any internet user can exploit this flaw without needing valid credentials. Once the malicious payload is stored in the database, it becomes active whenever a privileged user, such as an administrator or editor, accesses the relevant admin page where the data is displayed. This persistence mechanism ensures that the attack does not rely on social engineering to trick a specific user into clicking a link; instead, the vulnerability waits passively for legitimate administrative activity. If successful exploitation occurs against an account with elevated privileges, an attacker can gain full control over the WordPress installation. This includes the ability to steal session cookies and authentication tokens, perform actions on behalf of the administrator such as creating new admin users or modifying site settings, deface the website by altering content, or deploy further malware payloads like webshells for persistent remote access.
This vulnerability aligns with several well-defined industry standards that categorize common software weaknesses. It is primarily classified under CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. More specifically, because the malicious data is stored in a database or persistent storage and later retrieved for display without proper encoding, it falls squarely into the sub-category of Stored XSS. Additionally, the lack of access control on the endpoint that accepts the input relates to CWE-284, Improper Access Control, although the primary severity driver here is the injection flaw itself. In terms of offensive security frameworks like MITRE ATT&CK for Enterprise, this behavior corresponds to techniques involving Client-Side Injection and potentially Account Manipulation if used to escalate privileges or create backdoor accounts. The unauthenticated nature of the initial vector also touches upon aspects of Discovery and Initial Access depending on how the attacker leverages the stored payload in subsequent phases of an attack chain.
To mitigate this vulnerability, immediate remediation actions are required at both the code level and infrastructure level. Developers must implement strict input validation by whitelisting allowed characters or using robust sanitization libraries that strip out HTML tags and attributes associated with script execution before any data is written to the database. Equally important is the implementation of context-aware output encoding when rendering user-supplied content in admin interfaces, ensuring that special characters are converted into their corresponding HTML entities so they are treated as plain text rather than executable code. Upgrading to a patched version of the Ninja Forms click5 CRM add-on where these issues have been resolved by the vendor is the most effective long-term solution. In addition to software updates, administrators should enforce strong access controls and consider implementing Web Application Firewalls that can detect and block common XSS payloads in HTTP requests. Regular security audits and code reviews focusing on data flow from untrusted sources to sensitive outputs are essential practices to prevent similar injection flaws in future development cycles.