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DiscourseApplication

CVE-2026-33411

MEDIUM · 5.4 CVSS v3.1 Published 2026-03-20
Fix available
A fix is available. Upgrade to 2026.1.2 / 2026.2.1 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

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
Discourse is an open-source discussion platform. Versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 have a potential stored XSS in topic titles for the solved posts stream. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, ensure that the Content Security Policy is enabled, and has not been modified in a way which would make it more vulnerable to XSS attacks.

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

Discourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a stored XSS vulnerability in topic titles rendered within the solved posts stream feature. Attackers can inject malicious JavaScript through topic titles that persists in the database and executes when users view the solved posts stream.

MitigationUpgrade to version 2026.3.0-latest.1, 2026.2.1, or 2026.1.2. As a workaround, ensure Content Security Policy is enabled and properly configured to mitigate XSS risks.

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
DiscourseApplication
Affected:>= 2026.1.0, < 2026.1.2>= 2026.2.0, < 2026.2.1= 2026.3.0

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
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 checks

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

  1. Check Discourse version
    Access the Rails console or admin panel and run `Discourse::VERSION::STRING` or navigate to /admin/upgrade to view the installed version
    Affected if The installed version is 2026.1.0 through 2026.1.1, 2026.2.0 through 2026.2.0, or exactly 2026.3.0
  2. Verify solved plugin is enabled
    Navigate to Admin > Plugins or check the plugins directory for the 'discourse-solved' plugin being active
    Affected if The solved plugin is enabled and running an affected version from step 1
  3. Inspect topic titles in the database
    Query the database: `SELECT id, title FROM topics WHERE title LIKE '%<script%' OR title LIKE '%onerror=%' OR title LIKE '%javascript:%' OR title LIKE '%<img%' OR title LIKE '%onload=%';` or examine recent topics for suspicious title patterns
    Affected if Any topic titles contain unescaped HTML/JavaScript payloads such as script tags, event handlers, or javascript: URIs
  4. Review the solved posts stream output
    Navigate to a user's solved posts stream or the /solved endpoint and view page source to verify topic titles are properly escaped
    Affected if Topic titles in the solved posts stream render raw HTML instead of escaped text
  5. Check Content Security Policy
    Review the Discourse site settings for content_security_policy enabled status and review HTTP headers on responses from solved posts stream pages
    Affected if CSP is disabled and affected version is installed, increasing exploitability

If the installed Discourse version falls within 2026.1.0-2026.1.11, 2026.2.0-2026.2.0, or 2026.3.0 AND the solved plugin is active, the environment is likely affected by this stored XSS vulnerability.

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.

dbcve · scoped
Upgrade available Upgrade to 2026.1.2 / 2026.2.1 or later
Fixed in 2026.1.22026.2.1
Interim mitigation

Upgrade to version 2026.3.0-latest.1, 2026.2.1, or 2026.1.2. As a workaround, ensure Content Security Policy is enabled and properly configured to mitigate XSS risks.

Recommended fix High confidence

2026.1.2 (for 2026.1.x users), 2026.2.1 (for 2026.2.x users), or 2026.3.0-latest.1 (for 2026.3.x users)

  1. 1. Identify your current Discourse version by checking the admin panel or running `git log` in your installation directory
  2. 2. Based on your current version branch, upgrade to the appropriate fixed release:
  3. - If on 2026.1.x branch: upgrade to 2026.1.2
  4. - If on 2026.2.x branch: upgrade to 2026.2.1
  5. - If on 2026.3.x branch: upgrade to 2026.3.0-latest.1
  6. 3. Follow standard Discourse upgrade procedures for your deployment method (Docker, source, or package manager)
  7. 4. After upgrade, verify the installation by checking the version in the admin panel
  8. 5. Alternatively, as a configuration workaround if immediate upgrade is not possible: ensure Content Security Policy (CSP) is enabled in your Discourse configuration and has not been modified to allow unsafe-inline scripts

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Discourse Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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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-2026-33411 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