# CVE-2021-20664: Cross-site scripting in Movable Type

> Remote attackers can inject arbitrary scripts into the Asset registration screen of Movable Type, potentially compromising user sessions or executing malicious code.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A: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:** 5 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-pww3-vwvw-q638

## What is CVE-2021-20664?

CVE-2021-20664 is a medium-severity cross-site scripting vulnerability in Six Apart Ltd. Movable Type, published on 5 Mar 2021. 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

Cross-site scripting vulnerability in in Asset registration screen of Movable Type 7 r.4705 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.4705 and earlier (Movable Type Advanced 7 Series), Movable Type 6.7.5 and earlier (Movable Type 6.7 Series), Movable Type Premium 1.39 and earlier, and Movable Type Premium Advanced 1.39 and earlier allows remote attackers to inject an arbitrary script via unspecified vectors.

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

## Which versions are affected by CVE-2021-20664?

It affects 4 products.


Products: Movabletype Movable Type, Movabletype Movable Type Advanced, Movabletype Movable Type Premium, Movabletype Movable Type Premium Advanced.

## How do I fix CVE-2021-20664?

No fix has been published for CVE-2021-20664 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-20664 being exploited?

There is no known exploitation of CVE-2021-20664 in the wild and no public exploit code.

## Other vulnerabilities in Six Apart Ltd. Movable Type

- [CVE-2021-20663](https://insights.sbomify.com/CVE-2021-20663/): Cross-site scripting in Movable Type (medium 6.1)
- [CVE-2021-20665](https://insights.sbomify.com/CVE-2021-20665/): Cross-site scripting in Movable Type (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-20664 and fix it if it is affected.

What it is: CVE-2021-20664 is a medium-severity cross-site scripting vulnerability in Six Apart Ltd. Movable Type, published on 5 Mar 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-20664 in the wild and no public exploit code.

Affected product: Six Apart Ltd. Movable Type. 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-2021-20664/ (Markdown: https://insights.sbomify.com/CVE-2021-20664/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20664
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20664
- OSV: https://osv.dev/vulnerability/CVE-2021-20664

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20664/
Summaries are generated and may contain mistakes; the official description above is the record.