# CVE-2021-3313: Plone XSS in User Fullname Property and File Upload

> Stored XSS in Plone CMS allows attackers to execute JavaScript in victims' browsers via user fullname or file uploads.

- **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:** 20 May 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-hprr-4vfq-fcxw, PYSEC-2021-78

## What is CVE-2021-3313?

CVE-2021-3313 is a medium-severity cross-site scripting vulnerability in Plone Plone, published on 20 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 CMS until version 5.2.4 has a stored Cross-Site Scripting (XSS) vulnerability in the user fullname property and the file upload functionality. The user's input data is not properly encoded when being echoed back to the user. This data can be interpreted as executable code by the browser and allows an attacker to execute JavaScript in the context of the victim's browser if the victim opens a vulnerable page containing an XSS payload.

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

## Which versions are affected by CVE-2021-3313?

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 | 5.2.4 |
| `plone` | PyPI | All versions | 5.2.4 |
| `Plone` | PyPI | All versions | 5.2.4 |

Products: Plone Plone.

## How do I fix CVE-2021-3313?

Upgrade plone to 5.2.4 or later.

## Is CVE-2021-3313 being exploited?

There is no known exploitation of CVE-2021-3313 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-2021-3313 and fix it if it is affected.

What it is: CVE-2021-3313 is a medium-severity cross-site scripting vulnerability in Plone Plone, published on 20 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-2021-3313 in the wild and no public exploit code.

Affected packages and fixed versions:
- plone (PyPI): affected all versions; fixed in 5.2.4
- plone (PyPI): affected all versions; fixed in 5.2.4
- Plone (PyPI): affected all versions; fixed in 5.2.4

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-2021-3313/ (Markdown: https://insights.sbomify.com/CVE-2021-3313/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3313
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3313
- OSV: https://osv.dev/vulnerability/CVE-2021-3313

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3313/
Summaries are generated and may contain mistakes; the official description above is the record.