Nextcloud ServerApplication · Nextcloud
CVE-2018-3780
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 sanitization of search results for an autocomplete field in NextCloud Server <13.0.5 could lead to a stored XSS requiring user-interaction. The missing sanitization only affected user names, hence malicious search results could only be crafted by authenticated users.
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 · high confidenceA stored XSS vulnerability in NextCloud Server versions before 13.0.5 exists due to missing sanitization of autocomplete search results for usernames. Authenticated users can inject malicious JavaScript into their username, which executes when other users interact with the autocomplete field and select the crafted username.
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
< 13.0.5CVSS 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:3.0/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 installed NextCloud versionCheck the NextCloud admin panel under Settings > Administration > Overview, or examine the version.php file in the NextCloud installation directoryAffected if The installed version is any release before 13.0.5 (e.g., 13.0.4, 13.0.0-13.0.4, 12.x, 11.x)
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Confirm autocomplete feature is accessibleVerify that the username autocomplete functionality is available in the web interface, typically triggered when typing usernames in sharing dialogs, comments, or user mention fieldsAffected if The autocomplete feature is present and accessible to authenticated users in the environment
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Inspect stored usernames for XSS payloadsQuery the oc_users or similar user table in the NextCloud database to examine username values, looking for HTML/script tags, event handlers, or encoded characters that may contain malicious codeAffected if Any username in the database contains unsanitized JavaScript or HTML markup that could execute when rendered in autocomplete results
You are affected if your NextCloud Server version is before 13.0.5 and any user account contains a username with embedded script or HTML tags that would execute when displayed in autocomplete results.
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 data13.0.5
Upgrade to NextCloud Server 13.0.5 or later which includes proper HTML entity encoding of usernames in autocomplete search results. User interaction is required for exploitation.
Fix this in Nextcloud Server
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-3780 — 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-2018-3780 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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