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Medium Severity

Open redirect: Xfinity CMP Redirection to Google AMP

Description

Detects when non-Xfinity senders abuse Xfinity's CMP redirection service to reach Google AMP pages. The rule specifically looks for targetURL parameters containing Google AMP paths in links from untrusted or previously malicious senders.

References

No references.

Sublime Security
Created Jan 3rd, 2025 • Last updated Aug 5th, 2025
Source
type.inbound
and any(body.links,
        .href_url.domain.domain == "cmp.cws.xfinity.com"
        and strings.icontains(.href_url.query_params, "&targetURL=")
        and regex.icontains(.href_url.query_params,
                            '&targetUrl=(?:https?)?(?:(?:%3a|\:)?(?:\/|%2f){2})?google\.[^\&]*\/+amp\/+s\/+'
        )
)
and not sender.email.domain.root_domain in ("xfinity.com", "comcast.net")

// 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
)
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