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Mattermost ServerApplication · Mattermost

CVE-2016-11071

MEDIUM · 6.1 CVSS v3.1 Published 2020-06-19
Fix available
A fix is available. Upgrade to 3.1.0 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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 · unedited
An issue was discovered in Mattermost Server before 3.1.0. It allows XSS because the noreferrer and noopener protection mechanisms were not in place.

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 confidence

Mattermost Server before 3.1.0 contains a cross-site scripting vulnerability where external links with target='_blank' lack the rel='noopener noreferrer' attributes. This allows opened pages to access and manipulate the originating page via window.opener, enabling phishing or script injection attacks.

MitigationAdd rel='noopener noreferrer' to all external links that use target='_blank' across the application, particularly in user-generated content rendering and notification links.

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
Mattermost ServerApplication
Affected:< 3.1.0

CVSS 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
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed Mattermost Server version
    Access the Mattermost admin console or system information page to find the current version number. This is typically available in the About section or System Console.
    Affected if The installed version is lower than 3.1.0
  2. Examine external links in user-generated content
    Inspect the HTML rendering of user posts, comments, or messages containing hyperlinks. Look for anchor tags with the target='_blank' attribute.
    Affected if External links with target='_blank' are present in rendered user content
  3. Check rel attribute on new window links
    View the source or inspect elements of links that have target='_blank' to verify if the rel attribute includes 'noopener noreferrer'.
    Affected if Links with target='_blank' are missing the rel='noopener noreferrer' attribute

The environment is affected if running Mattermost Server version below 3.1.0 and external links with target='_blank' do not include rel='noopener noreferrer' attributes.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 3.1.0 or later
Fixed in 3.1.0
Interim mitigation

Add rel='noopener noreferrer' to all external links that use target='_blank' across the application, particularly in user-generated content rendering and notification links.

Fix this in Mattermost Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-11071 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data