Medium Severity

Attachment: ICS calendar invite with Google share.google URL shortener in google.<tld>/share.google path form

Description

Detects inbound messages with ICS calendar invites containing links in the form google.<tld>/share.google?q=<code>, which inherits google.<tld> domain reputation to mask an attacker-controlled destination. This google.<tld>/share.google?q= path form is undocumented: Google publishes the share.google shortener feature, but not this on-Google-domain form or its 'q' parameter.

References

No references.

Sublime Security
Created Sep 14th, 2026 • Last updated Sep 14th, 2026
Source
type.inbound
and any(attachments,
        (
          .file_type == "ics"
          or .file_extension == "ics"
          or .content_type in ("application/ics", "text/calendar")
        )
        //
        // This rule makes use of a beta feature and is subject to change without notice
        // using the beta feature in custom rules is not suggested until it has been formally released
        //
        and any(beta.file.parse_ics(.).events,
                any(.links,
                    .href_url.domain.sld == "google"
                    and strings.istarts_with(.href_url.path, '/share.google')
                    and 'q' in keys(.href_url.query_params_decoded)
                )
        )
)
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