CVE-2026-18478 in Magnolia
Summary
by MITRE • 08/10/2026
Magnolia CMS is vulnerable to Stored XSS in import functionality. An attacker with editor privileges can inject arbitrary HTML and JS into the name of uploaded image, which will be rendered/executed when opening uploaded image.
The issue was fixed in version 6.3.10
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Analysis
by VulDB Data Team • 08/10/2026
Magnolia CMS stored cross-site scripting vulnerability in its import functionality represents a significant security risk that leverages the platform's content management capabilities to execute malicious code. This vulnerability specifically affects users with editor privileges who can upload images through the system's import mechanisms. The flaw occurs when the application fails to properly sanitize user-supplied input during the image naming process, allowing attackers to inject arbitrary HTML and JavaScript code directly into the filename field. When other users subsequently view or interact with these uploaded images, the malicious code executes in their browser context, potentially compromising their sessions or executing unauthorized actions.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding within Magnolia's image import handling routines. When an editor uploads an image, the system processes the filename without sufficient sanitization measures to prevent script injection attempts. This weakness creates a persistent vector for attackers to embed malicious payloads that can exploit the trust relationship between users and the CMS platform. The vulnerability operates as a classic stored XSS attack where the malicious code is stored on the server and executed whenever the compromised content is accessed, making it particularly dangerous for widespread impact.
The operational implications of this vulnerability extend beyond simple script execution to encompass potential session hijacking, credential theft, and unauthorized administrative actions. Attackers could craft malicious filenames that redirect users to phishing sites, steal authentication cookies, or inject additional malicious scripts that persist across user sessions. The fact that this requires only editor privileges makes the attack surface particularly concerning as it can be exploited by users who have legitimate access to content management functions but not necessarily administrative rights. This creates a scenario where internal threats or compromised accounts with editor permissions can escalate their privileges through client-side exploitation.
Organizations using Magnolia CMS should prioritize immediate mitigation through the available patch version 6.3.10 which addresses the input validation issues in the import functionality. System administrators should also implement additional defensive measures including enhanced monitoring of upload activities, regular security scanning of uploaded content, and restriction of editor privileges to trusted users only. The vulnerability aligns with CWE-79 which identifies cross-site scripting flaws as a fundamental web application security weakness, and maps to ATT&CK technique T1566 related to spearphishing attachments that can be leveraged through compromised CMS platforms. Organizations should also consider implementing content security policies and input validation at multiple layers of their application architecture to prevent similar issues in other components.
The remediation process requires careful evaluation of existing uploads to identify potentially compromised content, especially images that may have been uploaded with malicious filenames before the patch was applied. Security teams should conduct comprehensive testing of the updated version to ensure that the fix properly addresses all input vectors and does not introduce regressions in legitimate functionality. Regular security assessments should include testing of import mechanisms and user privilege controls to prevent similar vulnerabilities from emerging in future releases, particularly focusing on proper sanitization of all user-supplied content before storage or rendering.