CVE-2026-44175 — getkirby / cms
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')TL;DR
This vulnerability affects all Kirby sites that use the list field or list block, when content is authored by users who may not be fully trusted. The attack requires an authenticated Panel user with update permission to any list field or list block.
This vulnerability is of high severity for affected sites.
Kirby sites are not affected if they don't use the list field (or blocks field with the list block) in any of their blueprints, or if every user who can edit content is fully trusted. The attack only surfaces in the site frontend (i.e. in the consuming project's templates). The Panel itself is unaffected and will not execute JavaScript that was injected into list field content.
Introduction
Cross-site scripting (XSS) is a type of vulnerability that allows to execute any kind of JavaScript code inside the site frontend or Panel session of the same or other users. In the Panel, a harmful script can for example trigger requests to Kirby's API with the permissions of the victim.
In a stored XSS attack, the malicious payload is saved into the content data and has the potential to affect other users or site visitors.
Such vulnerabilities are critical if applications might have potential attackers in their group of authenticated Panel users. They can escalate their privileges if they get access to the Panel session of an admin user. Depending on the site, other JavaScript-powered attacks are possible.
A specific class of stored XSS is auto-firing, meaning the malicious injected JavaScript code is executed by the browser when the page loads without the victim having to perform a specific action.
Affected components
Kirby's list field stores its formatted content as HTML code. Unlike with other field types, it is not possible to escape HTML special characters against cross-site scripting (XSS) attacks, otherwise the formatting would be lost.
Impact
In affected releases, Kirby did not securely sanitize the contents of list fields on save. This allowed attackers to inject malicious HTML code into the content file by sending it to Kirby's API directly without using the Panel. This malicious HTML code would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site.
Patches
The problem has been patched in Kirby 4.9.1 and Kirby 5.4.1. Please update to one of these or a later version to fix the vulnerability.
In all of the mentioned releases, Kirby has added HTML sanitization (like in the writer field) to the backend code that handles updates to the contents of list fields.
Credits
Kirby thanks @offset for responsibly reporting the identified issue.
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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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