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XenforoApplication

CVE-2026-35054

MEDIUM · 5.4 CVSS v3.1 Published 2026-04-01
Fix available
A fix is available. Upgrade to 2.3.9 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
XenForo before 2.3.9 is vulnerable to stored cross-site scripting (XSS) related to BB code rendering. An attacker can inject malicious scripts through BB code that are stored and executed when other users view the content.

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

XenForo before 2.3.9 contains a stored cross-site scripting (XSS) vulnerability in its BB code rendering system. Attackers can inject malicious JavaScript payloads through crafted BB code tags that get persisted to the database and execute in the browsers of users who view the affected content.

MitigationUpgrade to XenForo 2.3.9 or later to obtain the security patch. Until patched, consider restricting BB code usage or implementing output encoding on user-generated content.

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
XenforoApplication
Affected:< 2.3.9

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. Determine installed XenForo version
    Log into the XenForo admin control panel and navigate to the Dashboard or Options page to view the currently installed version number. Alternatively, check the version.php file in the library directory if filesystem access is available.
    Affected if The installed version is lower than 2.3.9
  2. Verify BB code rendering is enabled
    In the admin control panel, navigate to Options > BB code and confirm that BB code parsing is enabled for messages, signatures, or other user-generated content areas.
    Affected if BB code parsing is enabled on the forum
  3. Inspect custom BB code definitions
    In the admin control panel, review the Custom BB code section under BB code manager. Look for any custom BB codes that accept raw HTML, allow script tags, or have permissive template parsing that could be exploited.
    Affected if Custom BB codes exist with insecure template configurations
  4. Search database for suspicious BB code patterns
    Query the database (xf_post, xf_profile_post, or similar tables depending on your setup) for BB code content containing potentially malicious patterns such as script tags, javascript: URIs, or event handler attributes within BB code tags. Use SQL such as: SELECT * FROM xf_post WHERE message LIKE '%[script%' OR message LIKE '%onload=%'.
    Affected if Records contain crafted BB code tags with embedded script or event handler payloads
  5. Review recent user registrations and content
    Check recent posts, signatures, and profile posts for unfamiliar or suspicious BB code usage, particularly from new accounts or accounts with elevated privileges.
    Affected if User-generated content contains unexpected BB code that may contain malicious payloads

A XenForo installation is affected if it runs any version lower than 2.3.9 and has BB code rendering enabled, as attackers can inject XSS payloads through crafted BB code tags stored in the database.

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 2.3.9 or later
Fixed in 2.3.9
Interim mitigation

Upgrade to XenForo 2.3.9 or later to obtain the security patch. Until patched, consider restricting BB code usage or implementing output encoding on user-generated content.

Recommended fix High confidence

XenForo 2.3.9

  1. Verify current XenForo installation version in admin control panel under "Basic board information"
  2. Download XenForo 2.3.9 from the official XenForo member area or your customer account
  3. Create a full backup of the database and files before proceeding with the upgrade
  4. Upload the new 2.3.9 files to your server, overwriting existing files
  5. Run the upgrade script by accessing your forum URL (the system will automatically detect and apply updates)
  6. Clear all caches via admin control panel > Tools > Rebuild caches
  7. Verify the upgrade was successful by checking the version number in the admin control panel
  8. Test BB code rendering in posts to confirm the XSS fix is working
Caveat Review XenForo 2.3.9 release notes for any template modifications or add-on compatibility notices before upgrading

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

Fix this in Xenforo Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,224.

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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-2026-35054 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