Analysis of Modern Web Penetration Techniques and Proactive Defense Mechanisms

With the rapid development of web applications, cybersecurity threats have demonstrated trends of diversification and increasing sophistication. This paper focuses on four typical web security risks: Cross-Site Scripting (XSS), SQL injection, broken authentication, and file upload vulnerabilities. Through systematic analysis of attack principles, vulnerability code validation, and reconstruction of defense mechanisms, it reveals the formation mechanisms of attack chains and critical weaknesses in existing security protections. The research employs case studies, code reproduction, and penetration testing methodologies, demonstrating the limitations of traditional approaches including blacklist filtering, client-side validation, and plaintext transmission. Based on these findings, a multi-dimensional defense strategy is proposed: For XSS attacks, comprehensive protection requires integrated input filtering, output encoding, and Content Security Policy (CSP); SQL injection prevention mandates enforced parameterized queries and prepared statements; broken authentication mitigation necessitates enhanced password hashing algorithms, robust session management, and HTTPS encryption; file upload vulnerabilities demand defense-in-depth through whitelist validation, path isolation, and strict permission controls. This research provides a systematic solution spanning from attack pathway disruption to security architecture enhancement, offering significant practical guidance for secure development practices.