The document discusses vulnerable web applications as a serious threat vector for attackers. It analyzes data from over 900 web application scans conducted in 2013 which found that injection attacks, broken authentication, and cross-site scripting were still common issues. Broken authentication, such as failing to update session IDs during login, was one of the most prevalent issues, putting sites at risk for session fixation attacks. The document provides tips for safe production scanning and ensuring proper test coverage to identify vulnerabilities before applications are deployed.