Summary
Cross-site Scripting vulnerabilities in Neos
It has been discovered that Neos is vulnerable to several XSS attacks. Through these vulnerabilities, an attacker could tamper with page rendering, redirect victims to a fake login page, or capture user credentials (such as cookies). With the potential backdoor upload an attacker could gain access to the server itself, to an extent mainly limited by the server setup.
Reflected Cross-Site Scripting (SXSS) with authentication
A Neos backend user with permission to modify content can insert JavaScript instructions into content elements. The browser will execute the script in "Print" preview mode.
A Neos backend user who can modify his profile information ("Title", "First Name", "Last name", "Middle Name", "Other Name") can inject JavaScript instructions in those parameters. Once set up, an administrator who wants to edit this user account will execute the code.
Both attack vectors require a valid Neos backend user account.
Reflected Cross-Site Scripting (RXSS) without authentication
A non-persistent XSS using parameters passed during plugin execution is possible. If invalid parameters are passed, an error message may be shown (depending on the context Neos runs in and how the parameters are handled) that contains the unescaped parameter value.
Note: Through the HTML content type the inclusion of arbitrary JavaScript is still possible for users with a valid Neos backend account. If you want to prohibit that, disable the nodetype or restrict access.
Potential backdoor upload
Through an issue with the underlying Flow framework (see the related Flow advisory Flow-SA-2015-001) any editor with access to the Media Management module can upload server side script files (when using Neos 2.0.x). If those scripts are executed by the server when accessed through their public URL, anything not blocked through other means is possible (information disclosure, placement of backdoors, data removal, …).
Impact
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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neos/neos to 1.2.13 or later; neos/neos to 2.0.4 or later
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Frequently Asked Questions
- What is GHSA-6CJ3-RC4P-F38F? GHSA-6CJ3-RC4P-F38F is a high-severity cross-site scripting (XSS) vulnerability in neos/neos (composer), affecting versions >= 1.2.0, < 1.2.13. It is fixed in 1.2.13, 2.0.4. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of neos/neos are affected by GHSA-6CJ3-RC4P-F38F? neos/neos (composer) versions >= 1.2.0, < 1.2.13 is affected.
- Is there a fix for GHSA-6CJ3-RC4P-F38F? Yes. GHSA-6CJ3-RC4P-F38F is fixed in 1.2.13, 2.0.4. Upgrade to this version or later.
- Is GHSA-6CJ3-RC4P-F38F exploitable, and should I be worried? Whether GHSA-6CJ3-RC4P-F38F 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 GHSA-6CJ3-RC4P-F38F 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 GHSA-6CJ3-RC4P-F38F?
- Upgrade
neos/neosto 1.2.13 or later - Upgrade
neos/neosto 2.0.4 or later
- Upgrade