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DiscourseApplication

CVE-2026-27154

MEDIUM · 6.1 CVSS v3.1 Published 2026-02-26
Fix available
A fix is available. Upgrade to 2025.12.2 / 2026.1.1 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
Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, a user full name can be evaluated as raw HTML when the following settings are set: `display_name_on_posts` => true; and `prioritize_username_in_ux` => false. Editing a post of a malicious user would trigger an XSS. Versions 2025.12.2, 2026.1.1, and 2026.2.0 patch the issue. No known workarounds are available.

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

This is a stored XSS vulnerability in Discourse where a malicious user's full name is rendered as raw HTML instead of being sanitized. The vulnerability only triggers when two specific settings are enabled: `display_name_on_posts` is true and `prioritize_username_in_ux` is false. An attacker can inject malicious JavaScript via their full name, which executes when another user edits the attacker's post.

MitigationUpgrade Discourse to version 2025.12.2, 2026.1.1, or 2026.2.0 which contain the patch for this vulnerability. There are no available workarounds.

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:< 2025.12.2>= 2026.1.0, < 2026.1.1= 2026.2.0

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. Check Discourse version
    Access the Discourse admin panel and navigate to /admin/about or run `discourse --version` from the command line
    Affected if The installed version is < 2025.12.2, OR >= 2026.1.0 AND < 2026.1.1, OR exactly 2026.2.0
  2. Verify display_name_on_posts setting
    In Discourse admin panel, go to Settings > Posting and look for the `display_name_on_posts` setting, or query the site settings via API: GET /site.json
    Affected if The setting `display_name_on_posts` is enabled (set to true)
  3. Verify prioritize_username_in_ux setting
    In Discourse admin panel, go to Settings > Users and look for the `prioritize_username_in_ux` setting, or query via API
    Affected if The setting `prioritize_username_in_ux` is disabled (set to false)
  4. Inspect user full names for malicious content
    Query the database: SELECT id, username, name FROM users WHERE name LIKE '%<%' OR name LIKE '%javascript:%' OR name LIKE '%onload%' OR name LIKE '%onerror%'; or review user profiles in admin panel for unsanitized HTML in full name fields
    Affected if Any user account has a full name containing raw HTML tags, script tags, or javascript: protocol handlers

A user is affected if they are running a vulnerable Discourse version AND have display_name_on_posts enabled AND have prioritize_username_in_ux disabled AND a malicious user exists with unsanitized HTML in their full name field.

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 2025.12.2 / 2026.1.1 or later
Fixed in 2025.12.22026.1.1
Interim mitigation

Upgrade Discourse to version 2025.12.2, 2026.1.1, or 2026.2.0 which contain the patch for this vulnerability. There are no available workarounds.

Recommended fix High confidence

2026.2.0 (or latest stable: 2025.12.2+ / 2026.1.1+ / 2026.2.0+)

  1. Check current Discourse version via admin panel or CLI
  2. Identify the affected version branch currently running
  3. Upgrade to version 2025.12.2 (if on older branch), 2026.1.1 (if on 2026.1.x branch), or 2026.2.0 (if on 2026.2.x branch)
  4. For production environments, backup database before upgrading
  5. Execute standard Discourse upgrade procedure (./launcher rebuild app for Docker installations)
  6. Verify successful upgrade by confirming new version number
  7. Confirm the XSS vulnerability is resolved by editing a post with a crafted full name

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

Fix this in Discourse Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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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-2026-27154 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