Open redirect: Club-OS

name: "Open redirect: Club-OS"
description: |
  Message contains use of the Club-OS open redirect. This has been exploited in the wild.
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(body.links,
          .href_url.domain.root_domain == "club-os.com"
          and strings.icontains(.href_url.path, 'click')
          and strings.icontains(.href_url.query_params, 'target=')
          // negate hash lookup targets (not actor controlled)
          and not (
            regex.icontains(.href_url.query_params, 'target=[a-f0-9]{40}(?:$|&)')
            and strings.icontains(.href_url.query_params, '&hashLookup=true')
          )
          // negate urls that go back to club-os
          and not regex.icontains(.href_url.query_params,
                                  'target=[^\&]*club-os.com/'
          )
  )
  
  // negate highly trusted sender domains unless they fail DMARC authentication
  and (
    (
      sender.email.domain.root_domain in $high_trust_sender_root_domains
      and not headers.auth_summary.dmarc.pass
    )
    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Open redirect"
detection_methods:
  - "Sender analysis"
  - "URL analysis"
id: "c6286914-059d-5879-8f17-b923304cb628"