CVE-2020-36891
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA stored cross-site scripting vulnerability in Kentico Xperience allows attackers to upload files with spoofed Content-Type that do not match file extensions. Attackers can exploit this vulnerability by uploading malicious files with manipulated MIME types, allowing malicious scripts to execute in users' browsers.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA stored cross-site scripting vulnerability in Kentico Xperience allows attackers to upload files with spoofed Content-Type headers that don't match the actual file extensions. Attackers can upload malicious files (e.g., HTML or JavaScript files) with manipulated MIME types, enabling script execution in users' browsers when these files are accessed.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 12.0.49CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Kentico Xperience versionCheck the version in Kentico administration (About section or system settings), or look for version information in the installation directory and compare to the affected rangeAffected if Installed version is 12.0.49 or lower
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Confirm file upload functionality is enabledDetermine if media libraries, document attachments, or form file upload fields are available to users or content editors in the Kentico interfaceAffected if Any file upload capability is accessible to users
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Review file upload handler configurationInspect the server-side file upload handling code or configuration for validation that checks MIME types against file extensions and verifies actual file contentAffected if No strict server-side validation exists that enforces matching between file extensions and MIME types based on actual file content
The environment is affected if running Kentico Xperience version 12.0.49 or lower and has file upload functionality without proper server-side Content-Type validation.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedImplement strict server-side validation that enforces matching between file extensions and MIME types, including content-type validation based on actual file content (magic bytes) rather than client-provided headers.
Xperience 12.0.50 or later (latest 12.x hotfix)
- 1. Navigate to the Kentico Xperience administration interface
- 2. Go to the Applications or Settings area to check for system upgrades
- 3. Look for available updates to Xperience version 12.x
- 4. Apply the latest available hotfix or service pack for version 12.x that addresses security vulnerabilities
- 5. After applying the update, verify that file upload restrictions properly validate Content-Type headers against file extensions
- 6. Test the fix by attempting to upload a file with a mismatched Content-Type and ensure it is rejected or properly handled
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-36891 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-36891 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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