# CVE-2020-20691: File upload in n/a

> Attackers can execute arbitrary scripts by uploading crafted HTML files, bypassing extension filters in Monstra CMS.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-2648-mr6g-p443

## What is CVE-2020-20691?

CVE-2020-20691 is a medium-severity vulnerability in n/a, published on 27 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue in Monstra CMS v3.0.4 allows attackers to execute arbitrary web scripts or HTML via bypassing the file extension filter and uploading crafted HTML files.

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

## Which versions are affected by CVE-2020-20691?

It affects 1 product.


Products: Monstra Monstra Cms.

## How do I fix CVE-2020-20691?

No fix has been published for CVE-2020-20691 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-20691 being exploited?

There is no known exploitation of CVE-2020-20691 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-11678](https://insights.sbomify.com/CVE-2018-11678/): Security feature bypass in n/a (critical 9.8)
- [CVE-2025-69906](https://insights.sbomify.com/CVE-2025-69906/): File upload in n/a (high 8.8)
- [CVE-2020-23219](https://insights.sbomify.com/CVE-2020-23219/): Code injection in n/a (high 8.8)
- [CVE-2020-13978](https://insights.sbomify.com/CVE-2020-13978/): Command injection in n/a (high 7.2)
- [CVE-2018-11227](https://insights.sbomify.com/CVE-2018-11227/): Cross-site scripting in n/a (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-20691 and fix it if it is affected.

What it is: CVE-2020-20691 is a medium-severity vulnerability in n/a, published on 27 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-20691 in the wild and no public exploit code.

Affected product: n/a. 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-2020-20691/ (Markdown: https://insights.sbomify.com/CVE-2020-20691/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-20691
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-20691
- OSV: https://osv.dev/vulnerability/CVE-2020-20691

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-20691/
Summaries are generated and may contain mistakes; the official description above is the record.