# CVE-2021-39320: underConstruction <= 1.18 - Reflected Cross-Site Scripting

> Reflected XSS in underConstruction plugin allows attackers to inject scripts via request path on specific Apache configurations.

- **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:** 1 Sep 2021
- **Updated:** 5 May 2025
- **Also known as:** GHSA-p83h-qp2w-3vv5

## What is CVE-2021-39320?

CVE-2021-39320 is a medium-severity cross-site scripting vulnerability in Noah Kagan underConstruction, published on 1 Sep 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

The underConstruction plugin <= 1.18 for WordPress echoes out the raw value of `$GLOBALS['PHP_SELF']` in the ucOptions.php file. On certain configurations including Apache+modPHP, this makes it possible to use it to perform a reflected Cross-Site Scripting attack by injecting malicious code in the request path.

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

## Which versions are affected by CVE-2021-39320?

It affects 1 product.


Products: Underconstruction Project Underconstruction.

## How do I fix CVE-2021-39320?

No fix has been published for CVE-2021-39320 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-39320 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-39320 exists.

Public exploit code:

- WordPress Under Construction <1.19 - Cross-Site Scripting (nuclei): http/cves/2021/CVE-2021-39320.yaml

## Other vulnerabilities in Noah Kagan underConstruction

- [CVE-2013-2699](https://insights.sbomify.com/CVE-2013-2699/): Cross-site request forgery in n/a (medium 6.8)
- [CVE-2022-1896](https://insights.sbomify.com/CVE-2022-1896/): underConstruction < 1.21 - Admin+ Stored Cross-Site Scripting (medium 4.8)
- [CVE-2022-1895](https://insights.sbomify.com/CVE-2022-1895/): underConstruction < 1.20 - Construction Mode Deactivation via CSRF (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-39320 and fix it if it is affected.

What it is: CVE-2021-39320 is a medium-severity cross-site scripting vulnerability in Noah Kagan underConstruction, published on 1 Sep 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-39320 exists.

Affected product: Noah Kagan underConstruction. 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-2021-39320/ (Markdown: https://insights.sbomify.com/CVE-2021-39320/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-39320
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-39320
- OSV: https://osv.dev/vulnerability/CVE-2021-39320

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-39320/
Summaries are generated and may contain mistakes; the official description above is the record.