# CVE-2026-35055: XenForo Cross-Site Scripting via Lightbox in Posts

> Attackers can inject malicious scripts into XenForo posts that execute in victims' browsers when viewing lightbox content, potentially leading to session hijacking.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 1 Apr 2026
- **Updated:** 24 May 2026
- **Also known as:** GHSA-7285-3w46-g6m6

## What is CVE-2026-35055?

CVE-2026-35055 is a medium-severity cross-site scripting vulnerability in XenForo, published on 1 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-35055?

It affects 1 product.


Products: Xenforo Xenforo.

## How do I fix CVE-2026-35055?

No fix has been published for CVE-2026-35055 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-35055 being exploited?

There is no known exploitation of CVE-2026-35055 in the wild and no public exploit code.

## Other vulnerabilities in XenForo

- [CVE-2025-71279](https://insights.sbomify.com/CVE-2025-71279/): XenForo Passkey Security Bypass (critical 9.3)
- [CVE-2026-73309](https://insights.sbomify.com/CVE-2026-73309/): XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint (critical 9.1)
- [CVE-2026-73311](https://insights.sbomify.com/CVE-2026-73311/): XenForo < 2.3.13 OAuth2 Authorization Code Reuse (critical 9.1)
- [CVE-2026-73312](https://insights.sbomify.com/CVE-2026-73312/): XenForo < 2.3.13 Refresh Token Replay via Expired Access Token (critical 9.1)
- [CVE-2024-38457](https://insights.sbomify.com/CVE-2024-38457/): Xenforo before 2.2.16 allows CSRF. (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35055 and fix it if it is affected.

What it is: CVE-2026-35055 is a medium-severity cross-site scripting vulnerability in XenForo, published on 1 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-35055 in the wild and no public exploit code.

Affected product: XenForo. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-35055/ (Markdown: https://insights.sbomify.com/CVE-2026-35055/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35055
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35055
- OSV: https://osv.dev/vulnerability/CVE-2026-35055

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35055/
Summaries are generated and may contain mistakes; the official description above is the record.