CVE-2026-35054: XenForo Stored Cross-Site Scripting via BB Code Rendering

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-01 · updated 2026-06-17
Weakness: CWE-79

Description

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.

Affected products

XenForo: before 2.3.9 — fixed in 2.3.9

How to fix

Upgrade to a fixed version: XenForo 2.3.9. Check the vendor advisory for mitigations.

References

https://www.vulncheck.com/advisories/xenforo-stored-cross-site-scripting-via-bb-code-rendering
https://xenforo.com/community/threads/xenforo-2-3-9-inc-xfmg-2-2-18-released-security-fix.235659/

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