# CVE-2023-4021: Modern Events Calendar lite < 7.1.0 - Authenticated (Admin+) Stored Cross-Site Scripting

> Administrators can inject scripts via Google API settings in Modern Events Calendar Lite, affecting multi-site or restricted HTML installations.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Oct 2023
- **Updated:** 8 Apr 2026
- **Also known as:** GHSA-mxc9-v9vg-4xfw

## What is CVE-2023-4021?

CVE-2023-4021 is a medium-severity cross-site scripting vulnerability in webnus/ Modern Events Calendar Lite, published on 20 Oct 2023. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

The Modern Events Calendar lite plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Google API key and Calendar ID in versions up to, but not including, 7.1.0 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.

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

## Which versions are affected by CVE-2023-4021?

It affects 1 product.


Products: Webnus Modern Events Calendar Lite.

## How do I fix CVE-2023-4021?

No fix has been published for CVE-2023-4021 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-4021 being exploited?

There is no known exploitation of CVE-2023-4021 in the wild and no public exploit code.

## Other vulnerabilities in webnus/ Modern Events Calendar Lite

- [CVE-2021-24946](https://insights.sbomify.com/CVE-2021-24946/): Modern Events Calendar < 6.1.5 - Unauthenticated Blind SQL Injection (critical 9.8)
- [CVE-2021-24149](https://insights.sbomify.com/CVE-2021-24149/): Modern Events Calendar Lite < 5.16.6 - Authenticated SQL Injection (high 8.8)
- [CVE-2021-24146](https://insights.sbomify.com/CVE-2021-24146/): Modern Events Calendar Lite < 5.16.5 - Unauthenticated Events Export (high 7.5)
- [CVE-2021-24145](https://insights.sbomify.com/CVE-2021-24145/): Modern Events Calendar Lite < 5.16.5 - Authenticated Arbitrary File Upload leading to RCE (high 7.2)
- [CVE-2021-24925](https://insights.sbomify.com/CVE-2021-24925/): Modern Events Calendar Lite < 6.1.5 - Reflected Cross-Site Scripting (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-4021 and fix it if it is affected.

What it is: CVE-2023-4021 is a medium-severity cross-site scripting vulnerability in webnus/ Modern Events Calendar Lite, published on 20 Oct 2023. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-4021 in the wild and no public exploit code.

Affected product: webnus/ Modern Events Calendar Lite. 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-2023-4021/ (Markdown: https://insights.sbomify.com/CVE-2023-4021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-4021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-4021
- OSV: https://osv.dev/vulnerability/CVE-2023-4021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-4021/
Summaries are generated and may contain mistakes; the official description above is the record.