CVE-2025-53839 Overview
CVE-2025-53839 is a stored cross-site scripting (XSS) vulnerability in the DRACOON Branding Service. DRACOON is a file sharing platform, and the Branding Service allows customers to customize the DRACOON interface with their own brand assets. Versions prior to 2.10.0 improperly neutralize input supplied by administrative users, allowing HTML injection into the onboarding workflow presented to newly created users. The issue is tracked under [CWE-79] and was addressed in version 2.10.0. DRACOON rolled the fix out to the managed service, so customers do not need to take manual action.
Critical Impact
An administrative user can inject HTML into the onboarding flow of new users, enabling limited confidentiality and integrity impact across a changed security scope.
Affected Products
- DRACOON Branding Service versions prior to 2.10.0
- DRACOON tenants relying on the Branding Service for onboarding customization
- Managed DRACOON deployments before the vendor rollout of 2.10.0
Discovery Timeline
- 2025-07-15 - CVE-2025-53839 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in the NVD database
Technical Details for CVE-2025-53839
Vulnerability Analysis
The DRACOON Branding Service processes customization content supplied by tenant administrators and renders portions of that content inside the interface shown to end users during onboarding. Prior to version 2.10.0, the service failed to neutralize HTML markup in these administrator-controlled fields. An attacker with administrative access to the branding configuration can embed HTML, including script-bearing constructs, that is later delivered to newly onboarded users in the same tenant.
Exploitation requires an authenticated administrator, user interaction from the target, and produces limited confidentiality and integrity impact. Because the payload executes in the context of a different user session and can cross a trust boundary between the administrator and the onboarded user, the security scope changes during exploitation.
Root Cause
The root cause is improper neutralization of input during web page generation, classified as [CWE-79]. Branding fields accept HTML content from administrative users without sufficient sanitization or output encoding before that content is rendered in the onboarding workflow.
Attack Vector
The attack path requires an administrator to submit crafted branding content containing HTML markup. When a newly onboarded user loads the affected interface, the injected markup is parsed by the browser and executes in the user's session context. See the DRACOON GitHub Security Advisory GHSA-jv2h-8mw7-mc97 for vendor-published technical details.
Detection Methods for CVE-2025-53839
Indicators of Compromise
- Branding configuration entries containing HTML tags such as <script>, <img onerror=>, or <iframe> in fields that should be plain text or restricted markup
- Onboarding pages that render unexpected external resources or execute scripts from non-DRACOON origins
- Audit log entries showing branding updates from administrator accounts followed by user-reported UI anomalies
Detection Strategies
- Review DRACOON administrative audit logs for branding update events and correlate with the identity of the modifying administrator
- Inspect rendered onboarding pages for outbound requests to unknown domains that were not previously part of the tenant's branding configuration
- Monitor browser Content Security Policy (CSP) violation reports generated by users interacting with branded onboarding surfaces
Monitoring Recommendations
- Alert on any modification to branding assets or HTML-capable branding fields, particularly outside normal change windows
- Track privileged administrator sessions that touch the Branding Service and retain those events for post-incident review
- Baseline the expected DOM structure of onboarding pages and flag deviations that introduce script or iframe elements
How to Mitigate CVE-2025-53839
Immediate Actions Required
- Confirm that the DRACOON tenant is running Branding Service version 2.10.0 or later; the vendor rolled out the fix to the managed DRACOON service
- Audit recent branding configuration changes and revert any content that contains raw HTML or script constructs
- Review the administrator account inventory and remove branding privileges from accounts that do not require them
Patch Information
DRACOON released the fix in DRACOON Branding Service version 2.10.0. Per the vendor advisory, the update has been deployed to the DRACOON service, and customers of the managed offering do not need to take action. Operators of self-hosted or embedded deployments should verify that the running Branding Service version is 2.10.0 or later. Full details are published in the DRACOON GitHub Security Advisory.
Workarounds
- Restrict branding modification permissions to a minimal set of trusted administrators until version 2.10.0 is confirmed in place
- Require change review for any updates to branding fields that accept rich content
- Enforce a strict Content Security Policy at the tenant or reverse-proxy layer to limit script execution on onboarding pages
# Verify DRACOON Branding Service version (example against a tenant API)
curl -s https://<tenant>.dracoon.com/branding/api/v1/public/branding/info \
| grep -i version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
