Summary
Kirby CMS vulnerable to cross-site scripting (XSS) from list field content in the site frontend
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.
Credits
Kirby thanks @offset for responsibly reporting the identified issue.
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.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2026-44175? CVE-2026-44175 is a high-severity cross-site scripting (XSS) vulnerability in getkirby/cms (composer), affecting versions <= 4.9.0. It is fixed in 4.9.1, 5.4.1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of getkirby/cms are affected by CVE-2026-44175? getkirby/cms (composer) versions <= 4.9.0 is affected.
- Is there a fix for CVE-2026-44175? Yes. CVE-2026-44175 is fixed in 4.9.1, 5.4.1. Upgrade to this version or later.
- Is CVE-2026-44175 exploitable, and should I be worried? Whether CVE-2026-44175 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-44175 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-44175?
- Upgrade
getkirby/cmsto 4.9.1 or later - Upgrade
getkirby/cmsto 5.4.1 or later
- Upgrade