It's the most common vulnerability. Sysadmins are overworked. They spin up a new server and forget to change the default password, or leave the debug dashboard open to the internet.
The Debug Mode Disaster
You visit a website and trigger an error (entering ' in the search bar).
The site crashes and shows a full Python/Django stack trace.
This reveals: The server OS type, file paths (/var/www/html), library versions, and sometimes even Environment Variables (AWS Keys).
1. Default Accounts
Apache Tomcat: tomcat / s3cret
Jenkins: admin / admin
Routers: admin / password
Hackers run bots that scan the entire internet 24/7 trying these combinations.
2. Cloud Storage (S3 Buckets)
Leaving an AWS S3 bucket "Public".
Anyone with the URL can list all files and download customer data.
This is how Verizon leaked data on 6 million customers.
3. Directory Listing
If you visit http://site.com/images/ and see a list of files instead of a 403 Forbidden.
This helps hackers map your site structure and find backup files (database.bak) that you thought were hidden.
Hardening
1. Automate Hardening: Use Ansible/Chef to configure servers. Don't do it manually.
2. Disable Unused Features: Turn off ports, services, and accounts not in use.
3. Scan Yourself: Use OpenVAS or Nessus to find misconfigurations before hackers do.