Introduction In modern web infrastructures, organizations often use multiple third-party services like hosting platforms, CDNs, and SaaS tools. If these services are not configured properly, they can lead to a serious vulnerability known as Subdomain Takeover. This Subdomain Takeover guide 2026 explains how attackers identify misconfigured DNS records and how security professionals can prevent them. What is Subdomain Takeover Subdomain Takeover occurs when a subdomain points to an external service that is no longer active, but the DNS record still exists. An attacker can claim that external resource and gain control over the subdomain. Why It is Dangerous Full control over subdomain content Phishing attacks Cookie stealing Brand reputation damage How Subdomain Takeover Works A subdomain (e.g., test.example.com) points to a service (e.g., GitHub Pages) The service is deleted or inactive DNS record still exists Attacker registers the same service Attacker gains control of the subd...