# CVE-2021-33512: Cross-site scripting in Plone

> A Contributor can execute stored XSS attacks in Plone by uploading malicious SVG or HTML documents, potentially compromising user sessions.

- **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:** Yes
- **Published:** 21 May 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-hm2h-f456-6j88, PYSEC-2021-84

## What is CVE-2021-33512?

CVE-2021-33512 is a medium-severity cross-site scripting vulnerability in Plone Plone, published on 21 May 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Plone through 5.2.4 allows stored XSS attacks (by a Contributor) by uploading an SVG or HTML document.

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

## Which versions are affected by CVE-2021-33512?

3 open source packages ship an affected version, including plone and Plone. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `plone` | PyPI | All versions to 5.2.4 | None |
| `plone` | PyPI | All versions | 5.2.5 |
| `Plone` | PyPI | All versions to 5.2.4 | None |

Products: Plone Plone.

## How do I fix CVE-2021-33512?

Upgrade plone to 5.2.5 or later.

## Is CVE-2021-33512 being exploited?

There is no known exploitation of CVE-2021-33512 in the wild and no public exploit code.

## Other vulnerabilities in Plone Plone

- [CVE-2021-33509](https://insights.sbomify.com/CVE-2021-33509/): Incorrect Permission Assignment for Critical Resource in Plone (critical 9.9)
- [CVE-2020-35190](https://insights.sbomify.com/CVE-2020-35190/): Hardcoded credentials in n/a (critical 9.8)
- [CVE-2020-7941](https://insights.sbomify.com/CVE-2020-7941/): Plone Unauthenticated Write Vulnerability (critical 9.8)
- [CVE-2011-3587](https://insights.sbomify.com/CVE-2011-3587/): Zope Command Execution Vulnerability (critical 9.3)
- [CVE-2021-33926](https://insights.sbomify.com/CVE-2021-33926/): Server-Side Request Forgery in Plone CMS (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33512 and fix it if it is affected.

What it is: CVE-2021-33512 is a medium-severity cross-site scripting vulnerability in Plone Plone, published on 21 May 2021. 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-2021-33512 in the wild and no public exploit code.

Affected packages and fixed versions:
- plone (PyPI): affected all versions up to 5.2.4; no fix listed
- plone (PyPI): affected all versions; fixed in 5.2.5
- Plone (PyPI): affected all versions up to 5.2.4; 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-2021-33512/ (Markdown: https://insights.sbomify.com/CVE-2021-33512/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33512
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33512
- OSV: https://osv.dev/vulnerability/CVE-2021-33512

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33512/
Summaries are generated and may contain mistakes; the official description above is the record.