# CVE-2021-47836: Markdown Explorer 0.1.1 - Persistent Cross-Site Scripting

> Attackers can execute arbitrary code on the host by uploading markdown files with JavaScript payloads in Markdown Explorer.

- **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:** 16 Jan 2026
- **Updated:** 25 May 2026
- **Also known as:** GHSA-gj7m-5vcr-wh6x

## What is CVE-2021-47836?

CVE-2021-47836 is a medium-severity cross-site scripting vulnerability in jersou Markdown Explorer, published on 16 Jan 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

Markdown Explorer 0.1.1 contains a cross-site scripting vulnerability that allows attackers to inject malicious code through file uploads and editor inputs. Attackers can upload markdown files with embedded JavaScript payloads that execute in the application's privileged renderer context, allowing code execution on the host.

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

## Which versions are affected by CVE-2021-47836?


## How do I fix CVE-2021-47836?

No fix has been published for CVE-2021-47836 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-47836 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47836 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47836 and fix it if it is affected.

What it is: CVE-2021-47836 is a medium-severity cross-site scripting vulnerability in jersou Markdown Explorer, published on 16 Jan 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47836 exists.

Affected product: jersou Markdown Explorer. 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-2021-47836/ (Markdown: https://insights.sbomify.com/CVE-2021-47836/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47836
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47836
- OSV: https://osv.dev/vulnerability/CVE-2021-47836

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-47836/
Summaries are generated and may contain mistakes; the official description above is the record.