Open redirect: convertcart.com

name: "Open redirect: convertcart.com"
description: |
  Message contains use of the convertcart.com redirect. This has been exploited in the wild.
type: "rule"
severity: "medium"
source: |
  type.inbound
  // convertcart is used in benign messages, however, they commonly have many links
  // ensure messages contain less than 10 links convertcart.com to ensure higher fidelity matching of malicious messages
  and length(filter(body.links, .href_url.domain.root_domain == "convertcart.com")
  ) < 10
  and any(body.links,
          .href_url.domain.root_domain == "convertcart.com"
          and strings.iends_with(.href_url.path, '/click')
          and strings.icontains(.href_url.query_params, 'url=')
          and not regex.icontains(.href_url.query_params,
                                  'url=(?:https?(?:%3a|:))?(?:%2f|\/){2}[^&]*convertcart\.com(?:\&|\/|$|%2f)'
          )
          and not strings.icontains(.href_url.query_params,
                                    sender.email.domain.root_domain
          )
  )
  // remove uses that originate from convertcart.com
  and not any(headers.domains,
              .root_domain in ("convertcart.com", "convertc.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: "deab563d-bf41-5eed-84c0-2cac743675fc"