CVE-2026-57816 in Funnel Builder Plugin
Summary
by MITRE • 07/13/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in FunnelKit Funnel Builder by FunnelKit funnel-builder allows Reflected XSS.This issue affects Funnel Builder by FunnelKit: from n/a through <= 3.15.0.8.
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Analysis
by VulDB Data Team • 07/13/2026
Cross-site scripting vulnerabilities represent one of the most prevalent and dangerous web application security flaws, with reflected xss specifically targeting the injection of malicious scripts into web pages viewed by other users. This vulnerability in FunnelKit Funnel Builder creates a direct pathway for attackers to execute arbitrary javascript code within the context of legitimate user sessions, potentially compromising user data and system integrity. The flaw exists within the web page generation process where input parameters are not properly sanitized or encoded before being rendered back to users, allowing malicious payloads to persist in the application's response.
The technical implementation of this reflected xss vulnerability occurs when FunnelKit Funnel Builder processes user-supplied input through url parameters or form fields without adequate validation and output encoding. When vulnerable input reaches the web page generation phase, the application fails to neutralize potentially dangerous characters such as angle brackets, quotes, and javascript protocols that would normally be escaped or encoded to prevent execution. This improper handling creates an environment where attacker-controlled data can be interpreted as executable code by web browsers, enabling unauthorized actions including session hijacking, credential theft, and redirection to malicious sites. The vulnerability specifically affects versions up to and including 3.15.0.8, indicating a widespread issue within the affected product line that has not been fully addressed in these releases.
The operational impact of this reflected xss vulnerability extends beyond simple data exposure, as it enables attackers to manipulate user experiences and potentially gain elevated privileges within the application context. An attacker could craft malicious urls containing javascript payloads that would execute when users click on them, particularly in scenarios where users navigate to shared links or visit compromised websites. The reflected nature of this vulnerability means that the malicious script is not stored on the server but rather injected into the response by the application itself, making it difficult to detect through traditional security scanning methods. This type of vulnerability directly violates the principle of least privilege and can lead to complete compromise of user sessions, especially when combined with other attack vectors such as session management weaknesses or insufficient csrf protection mechanisms.
Mitigation strategies for this reflected xss vulnerability should focus on implementing comprehensive input validation and output encoding practices throughout the application's codebase. The primary defense mechanism involves ensuring that all user-supplied input is properly sanitized before being incorporated into web page content, with special attention to html entity encoding of characters such as < > & " ' and javascript protocols. Security controls should include implementing strict content security policies that prevent execution of inline scripts and restrict resource loading from untrusted sources. Additionally, the application should employ proper parameter validation techniques that reject or sanitize input containing potentially dangerous patterns, while also implementing robust session management controls to limit the impact of successful exploitation attempts. Organizations should also consider deploying web application firewalls and implementing regular security testing including automated scanning and manual penetration testing to identify and remediate similar vulnerabilities across their entire software portfolio, with particular emphasis on maintaining current versions of third-party components that may contain known security flaws.
This vulnerability aligns with common weakness enumeration 79 which specifically addresses cross-site scripting flaws in web applications, and represents a clear violation of the secure coding principles outlined in various cybersecurity frameworks. The attack pattern described corresponds to techniques documented in the attack tree framework where reflected xss serves as a foundational vector for more complex attacks including credential harvesting and privilege escalation scenarios, making it a critical target for remediation efforts within enterprise security programs.