XSS in Xenforo
CVE-2026-35055
XenForo before 2.3.9 and before 2.2.18 is vulnerable to cross-site scripting (XSS) related to lightbox usage in posts. An attacker can inject malicious scripts that execute when users interact with post content displayed in the lightbox.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (16.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 16.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Xenforo — versions 2.3.0, 0
Weakness classification (CWE)
References
- xenforo.com/community/threads/xenforo-2-3-9-inc-xfmg-2-2-18-released-security-f… (vendor-advisory, Release Notes, patch)
- www.vulncheck.com/advisories/xenforo-cross-site-scripting-via-lightbox-in-posts (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-35055?
- CVE-2026-35055 is a medium-severity vulnerability in Xenforo, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-01.
- How severe is CVE-2026-35055?
- Medium severity. CVSS v3 base score is 6.1 out of 10.