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Zulip ServerApplication · Zulip

CVE-2020-12759

MEDIUM · 6.1 CVSS v3.1 Published 2020-08-21
Fix available
A fix is available. Upgrade to 2.1.5 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
Zulip Server before 2.1.5 allows reflected XSS via the Dropbox webhook.

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 confidence

Zulip Server before version 2.1.5 contains a reflected XSS vulnerability in the Dropbox webhook integration. The webhook handler fails to properly sanitize or escape user-supplied input from Dropbox, allowing an attacker to inject malicious JavaScript that executes in the victim's browser when the crafted payload is reflected in the server's response.

MitigationUpgrade Zulip Server to version 2.1.5 or later, which contains the patch for this XSS vulnerability in the Dropbox webhook handler.

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
Zulip ServerApplication
Affected:< 2.1.5

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. Confirm Zulip Server is installed
    Run `zulip --version` or check for Zulip processes with `ps aux | grep zulip`
    Affected if Zulip Server is not found on the system
  2. Determine installed Zulip Server version
    Execute `zulip --version` and note the version number returned
    Affected if Version is below 2.1.5 (e.g., 2.1.4, 2.1.3, etc.)
  3. Check if Dropbox webhook integration is configured
    Look for Dropbox integration settings in Zulip admin settings at `/#` + navigate to Integrations > Dropbox, or search configuration files for 'dropbox'
    Affected if Dropbox webhook integration is enabled or configured in Zulip
  4. Verify webhook endpoint is accessible
    Check if the endpoint `/api/v1/external/dropbox` responds. This can be confirmed by reviewing the server's webhook routing configuration or attempting a request to the endpoint.
    Affected if The Dropbox webhook endpoint exists and accepts requests on the Zulip server

You are affected if your Zulip Server version is below 2.1.5 AND the Dropbox webhook integration has been configured or enabled on your server.

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 2.1.5 or later
Fixed in 2.1.5
Interim mitigation

Upgrade Zulip Server to version 2.1.5 or later, which contains the patch for this XSS vulnerability in the Dropbox webhook handler.

Fix this in Zulip Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.

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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-2020-12759 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