# CVE-2021-39341: OptinMonster <= 2.6.4 Unprotected REST-API Endpoints

> Attackers can access sensitive information and modify settings via unprotected REST API endpoints in the OptinMonster WordPress plugin.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Nov 2021
- **Updated:** 31 Mar 2025
- **Also known as:** GHSA-whcc-jgf3-q7pm

## What is CVE-2021-39341?

CVE-2021-39341 is a high-severity missing authorization vulnerability in OptinMonster, published on 1 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The OptinMonster WordPress plugin is vulnerable to sensitive information disclosure and unauthorized setting updates due to insufficient authorization validation via the logged_in_or_has_api_key function in the ~/OMAPI/RestApi.php file that can used to exploit inject malicious web scripts on sites with the plugin installed. This affects versions up to, and including, 2.6.4.

Weakness: CWE-319 (Cleartext Transmission of Sensitive Information), CWE-863 (Incorrect Authorization), CWE-285 (Improper Authorization)

## Which versions are affected by CVE-2021-39341?

It affects 1 product.


Products: Optinmonster Optinmonster.

## How do I fix CVE-2021-39341?

No fix has been published for CVE-2021-39341 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-39341 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-39341 exists.

Public exploit code:

- OptinMonster Plugin < 2.6.5 - Unprotected REST-API (nuclei): http/cves/2021/CVE-2021-39341.yaml

## Other vulnerabilities in OptinMonster

- [CVE-2023-0772](https://insights.sbomify.com/CVE-2023-0772/): Popup Builder by OptinMonster < 2.12.2 - Subscriber+ Arbitrary Post Content Disclosure (medium 6.5)
- [CVE-2024-4045](https://insights.sbomify.com/CVE-2024-4045/): Cross-site scripting in Popup Builder & Popup Maker for WordPress – OptinMonster Email Marketing and Lead Generation (medium 6.4)
- [CVE-2021-39325](https://insights.sbomify.com/CVE-2021-39325/): OptinMonster <= 2.6.0 Reflected Cross-Site Scripting (medium 6.1)
- [CVE-2016-10996](https://insights.sbomify.com/CVE-2016-10996/): Missing authorization in n/a (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-39341 and fix it if it is affected.

What it is: CVE-2021-39341 is a high-severity missing authorization vulnerability in OptinMonster, published on 1 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-39341 exists.

Affected product: OptinMonster. 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-2021-39341/ (Markdown: https://insights.sbomify.com/CVE-2021-39341/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-39341
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-39341
- OSV: https://osv.dev/vulnerability/CVE-2021-39341

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-39341/
Summaries are generated and may contain mistakes; the official description above is the record.