High Severity

Service abuse: Microsoft messaging with Cloudflare Turnstile-gated link

Description

Detects inbound messages sent through Microsoft's messaging.microsoft.com infrastructure containing links that reference the recipient's own domain in the URL. These links route through a Cloudflare Turnstile challenge, a technique used to block automated security scanners while still delivering the final payload to human victims.

References

No references.

Sublime Security
Created Oct 22nd, 2026 • Last updated Oct 23rd, 2026
Source
type.inbound
and sender.email.domain.domain == 'messaging.microsoft.com'
and any(filter(body.current_thread.links, .href_url.scheme != 'mailto'),
        strings.contains(.href_url.url, recipients.to[0].email.domain.domain)
        // CF Turnstile
        and any(ml.link_analysis(., mode="aggressive").unique_urls_accessed,
                .domain.domain == "challenges.cloudflare.com"
        )
)
MQL Rule Console
•Docs•Learning Labs

Playground

Test against your own EMLs or sample data.

Share

Post about this on your socials.

Get Started. Today.

Managed or self-managed. No MX changes.

Deploy and integrate a free Sublime instance in minutes.
Get Started