# CVE-2021-24826: Custom Content Shortcode < 4.0.2 - Authenticated Stored Cross-Site Scripting

> Authenticated users can inject malicious scripts via unescaped custom fields, allowing code execution in the context of other users.

- **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:** No
- **Published:** 7 Mar 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-h77p-7f34-7fqv

## What is CVE-2021-24826?

CVE-2021-24826 is a medium-severity cross-site scripting vulnerability in Unknown Custom Content Shortcode, published on 7 Mar 2022. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

The Custom Content Shortcode WordPress plugin before 4.0.2 does not escape custom fields before outputting them, which could allow Contributor+ (v < 4.0.1) or Admin+ (v < 4.0.2) users to perform Cross-Site Scripting attacks even when the unfiltered_html is disallowed. Please note that such attack is still possible by admin+ in single site blogs by default (but won't be when the unfiltered_html is disallowed)

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

## Which versions are affected by CVE-2021-24826?

It affects 1 product.


Products: Custom Content Shortcode Project Custom Content Shortcode.

## How do I fix CVE-2021-24826?

No fix has been published for CVE-2021-24826 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-24826 being exploited?

There is no known exploitation of CVE-2021-24826 in the wild and no public exploit code.

## Other vulnerabilities in Unknown Custom Content Shortcode

- [CVE-2023-0340](https://insights.sbomify.com/CVE-2023-0340/): Custom Content Shortcode <= 4.0.2 - Contributor+ LFI (high 8.8)
- [CVE-2023-0273](https://insights.sbomify.com/CVE-2023-0273/): Custom Content Shortcode <= 4.0.2 - Contributor+ Stored XSS (medium 5.4)
- [CVE-2021-24824](https://insights.sbomify.com/CVE-2021-24824/): Custom Content Shortcode < 4.0.1 - Unauthorised Arbitrary Post Metadata Access (medium 4.3)
- [CVE-2021-24825](https://insights.sbomify.com/CVE-2021-24825/): Custom Content Shortcode < 4.0.2 - Authenticated Arbitrary File Access / LFI (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-24826 and fix it if it is affected.

What it is: CVE-2021-24826 is a medium-severity cross-site scripting vulnerability in Unknown Custom Content Shortcode, published on 7 Mar 2022. 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-2021-24826 in the wild and no public exploit code.

Affected product: Unknown Custom Content Shortcode. 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-2021-24826/ (Markdown: https://insights.sbomify.com/CVE-2021-24826/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-24826
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-24826
- OSV: https://osv.dev/vulnerability/CVE-2021-24826

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-24826/
Summaries are generated and may contain mistakes; the official description above is the record.