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DiscourseApplication

CVE-2025-67723

MEDIUM · 5.4 CVSS v3.1 Published 2026-01-28
Fix available
A fix is available. Upgrade to 3.5.4 / 2025.11.2 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 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 have a content-security-policy-mitigated cross-site scriptinv vulnerability on the Discourse Math plugin when using its KaTeX variant. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. As a workaround, the Discourse Math plugin can be disabled, or the Mathjax provider can be used instead of KaTeX.

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

A cross-site scripting (XSS) vulnerability exists in the Discourse Math plugin when using the KaTeX rendering variant. This issue is mitigated by Content Security Policy, reducing its severity, but could still pose a risk in certain configurations. The vulnerability affects multiple older versions of Discourse.

MitigationUpdate to Discourse versions 3.5.4, 2025.11.2, 2025.12.1, or 2026.1.0 or later to patch this vulnerability. Alternatively, disable the Discourse Math plugin or switch to the Mathjax provider as a workaround.

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:< 3.5.4>= 2025.11.0, < 2025.11.2= 2025.12.0

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
    Navigate to /admin/docker or check the version file in your Discourse installation directory. The version is typically displayed in the admin panel footer or via the /about page.
    Affected if The installed version is < 3.5.4, or >= 2025.11.0 and < 2025.11.2, or exactly 2025.12.0
  2. Verify Math plugin is enabled
    Go to Admin > Plugins or check your app.yml for plugins listed with 'discourse-math'.
    Affected if The discourse-math plugin is installed and enabled
  3. Confirm KaTeX is the rendering provider
    Check the plugin settings at Admin > Plugins > discourse-math settings. Look for the 'math renderer' or 'provider' setting.
    Affected if The rendering provider is set to KaTeX (or the default, if KaTeX is the default)
  4. Check Content Security Policy configuration
    Review your site YAML configuration and Admin > Security > Content Security Policy for any custom CSP headers that might be weakening the default protections.
    Affected if CSP is disabled or significantly relaxed, allowing inline scripts

You are affected if your Discourse version is within the affected ranges AND the Math plugin is enabled with KaTeX as the provider, especially if CSP is disabled or relaxed.

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 3.5.4 / 2025.11.2 or later
Fixed in 3.5.42025.11.2
Interim mitigation

Update to Discourse versions 3.5.4, 2025.11.2, 2025.12.1, or 2026.1.0 or later to patch this vulnerability. Alternatively, disable the Discourse Math plugin or switch to the Mathjax provider as a workaround.

Recommended fix High confidence

2026.1.0 (or any of: 3.5.4, 2025.11.2, 2025.12.1)

  1. Upgrade Discourse to version 3.5.4, 2025.11.2, 2025.12.1, or 2026.1.0 to remediate the XSS vulnerability in the Discourse Math plugin KaTeX variant
  2. As an alternative if immediate upgrade is not feasible, disable the Discourse Math plugin entirely
  3. Alternatively, switch the math provider from KaTeX to Mathjax in the Discourse Math plugin settings

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

Fix this in Discourse Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
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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-2025-67723 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