# CVE-2023-6551: Stored XSS in class.upload.php

> Stored XSS in class.upload.php allows attackers to inject scripts via uploaded files, requiring developers to implement extension whitelisting and content-type enforcement.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 4 Jan 2024
- **Updated:** 3 Jun 2025
- **Also known as:** GHSA-v6f4-jwv9-682w

## What is CVE-2023-6551?

CVE-2023-6551 is a medium-severity cross-site scripting vulnerability in class.upload.php, published on 4 Jan 2024. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

As a simple library, class.upload.php does not perform an in-depth check on uploaded files, allowing a stored XSS vulnerability when the default configuration is used. 

Developers must be aware of that fact and use extension whitelisting accompanied by forcing the server to always provide content-type based on the file extension. 

The README has been updated to include these guidelines.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type)

## Which versions are affected by CVE-2023-6551?

2 open source packages ship an affected version, including verot/class.upload.php. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `verot/class.upload.php` | Packagist | All versions to 2.1.6 | None |
| `verot/class.upload.php` | Packagist | All versions to 2.1.6 | None |

Products: Verot Class.upload.php.

## How do I fix CVE-2023-6551?

No fix has been published for CVE-2023-6551 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-6551 being exploited?

There is no known exploitation of CVE-2023-6551 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-6551 and fix it if it is affected.

What it is: CVE-2023-6551 is a medium-severity cross-site scripting vulnerability in class.upload.php, published on 4 Jan 2024. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-6551 in the wild and no public exploit code.

Affected packages and fixed versions:
- verot/class.upload.php (Packagist): affected all versions up to 2.1.6; no fix listed
- verot/class.upload.php (Packagist): affected all versions up to 2.1.6; no fix listed

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-2023-6551/ (Markdown: https://insights.sbomify.com/CVE-2023-6551/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6551
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6551
- OSV: https://osv.dev/vulnerability/CVE-2023-6551

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6551/
Summaries are generated and may contain mistakes; the official description above is the record.