CVE-2026-17037 in Kirki Plugin
Summary
by MITRE • 09/11/2026
The Kirki – Freeform Page Builder, Website Builder & Customizer plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘comment’ parameter in all versions up to, and including, 6.2.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified within the Kirki – Freeform Page Builder plugin for WordPress represents a significant security risk due to its potential for Stored Cross-Site Scripting, commonly referred to as XSS. This flaw exists across all versions up to and including 6.2.0 and is primarily triggered through the comment parameter. The root cause of this vulnerability lies in insufficient input sanitization and output escaping mechanisms within the plugin's codebase. When a user submits data via the comment field, the application fails to adequately validate or sanitize the incoming information before storing it in the database. Furthermore, when this stored data is subsequently rendered on web pages for other users to view, the system does not properly escape special characters that could be interpreted as executable script commands by the browser.
This architectural deficiency allows unauthenticated attackers to inject arbitrary web scripts into the application's content. Unlike reflected XSS attacks where malicious code is executed only when a victim clicks a specially crafted link, stored XSS persists on the server side. Once an attacker successfully injects their payload through the vulnerable comment parameter, the malicious script becomes part of the page content itself. Consequently, every user who accesses the affected page will have the injected scripts execute in their browser session without any additional interaction required from them beyond viewing the page. This persistence makes stored XSS particularly dangerous as it can affect a large number of victims automatically and repeatedly over time.
The operational impact of this vulnerability is severe, potentially leading to complete compromise of user accounts and sensitive data exposure. When malicious scripts execute in the context of an authenticated user's session, they inherit that user's privileges. Attackers can utilize these scripts to steal session cookies, which may allow them to hijack active sessions and impersonate legitimate users. Additionally, attackers could perform actions on behalf of victims, such as modifying settings, deleting content, or installing further malicious plugins if the victim has administrative rights. In many cases, stored XSS is also used for phishing attacks where fake login forms are injected into pages to harvest credentials from unsuspecting visitors. The ability to execute arbitrary JavaScript means that attackers can manipulate page content dynamically, deface websites, or redirect users to malicious sites designed to distribute malware.
From a classification perspective, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation known as Cross-site Scripting. The specific nature of the attack vector where data is stored and later retrieved for display corresponds closely to ATT&CK technique T1059, specifically sub-technique 007 involving JavaScript execution in web browsers. Understanding these mappings helps security professionals categorize the risk accurately within broader threat intelligence frameworks and ensures that mitigation strategies address both the technical flaw and its tactical implications.
To mitigate this vulnerability, immediate action is required to update the Kirki plugin to a version newer than 6.2.0 where the issue has been resolved by developers through proper input validation and output encoding practices. For organizations unable to upgrade immediately due to compatibility constraints or other operational reasons, implementing Web Application Firewall rules can provide temporary protection by detecting and blocking requests containing known XSS payloads in comment fields. Additionally, enforcing Content Security Policy headers that restrict script execution sources can limit the impact of any successfully injected scripts by preventing them from loading external resources or executing inline code unless explicitly allowed. Regular security audits and penetration testing should be conducted to identify similar flaws in other plugins and custom themes, ensuring a holistic approach to WordPress site hardening against injection-based attacks.