Nextcloud ServerApplication · Nextcloud
CVE-2020-8294
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 missing link validation in Nextcloud Server before 20.0.2, 19.0.5, 18.0.11 allows execution of a stored XSS attack using Internet Explorer when saving a 'javascript:' URL in markdown format.
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 confidenceNextcloud Server has a stored XSS vulnerability caused by missing link validation. Attackers can inject 'javascript:' URLs into markdown content, which executes malicious JavaScript when the document is viewed in Internet Explorer.
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
Nextcloud ServerApplication
< 18.0.11>= 19.0.0, < 19.0.5>= 20.0.0, < 20.0.2CVSS 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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Determine your Nextcloud Server versionLog into the Nextcloud admin panel and navigate to 'Settings' > 'Administration' > 'Overview', or check the version file at /version.php in the Nextcloud root directoryAffected if The installed version falls within < 18.0.11, >= 19.0.0 and < 19.0.5, or >= 20.0.0 and < 20.0.2
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Identify if markdown content existsCheck if the Nextcloud Notes app or any app storing markdown (.md) files is enabled. Query the database table oc_appconfig for app_id='notes' and value='yes', or inspect user data directories for .md filesAffected if Markdown functionality is active and users can create or import markdown content
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Search for javascript: URLs in stored contentSearch the Nextcloud database (table oc_notes_meta or oc_filecache) for entries containing 'javascript:' using SQL: SELECT * FROM oc_notes_meta WHERE body LIKE '%javascript:%'Affected if Any stored content contains 'javascript:' URL strings, indicating potential exploit payload
You are affected if your Nextcloud Server version is below 18.0.11, between 19.0.0-19.0.5, or between 20.0.0-20.0.2 AND you have markdown content that could contain injected 'javascript:' URLs viewed in Internet Explorer
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.
From vendor data18.0.1119.0.520.0.2
Upgrade to Nextcloud Server 20.0.2, 19.0.5, 18.0.11 or later which adds proper link validation to reject 'javascript:' URLs in markdown. Alternatively, restrict or disable markdown functionality until patching is possible.
Fix this in Nextcloud Server
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-8294 — 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-2020-8294 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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