Exposed Subdomains
1-minute read
Short definition
Exposed subdomains are publicly accessible subdomains that reveal services, applications, or environments not intended for external access.
What it is
Subdomains such as dev.example.com, test.example.com, or old.example.com are often created for development, testing, or legacy systems. When left exposed, they may run outdated software, lack authentication, or bypass security controls applied to the main domain.
Why it matters
Attackers routinely enumerate subdomains to find weak entry points. An exposed subdomain can leak sensitive data, expose admin panels, or provide a foothold into internal systems. Many high-impact breaches start with a forgotten or misconfigured subdomain.
How to reduce risk
- Perform regular subdomain discovery and audits
- Decommission unused or legacy subdomains
- Apply the same security controls as production systems
- Restrict access to development and staging environments
- Continuously monitor DNS and certificate transparency logs