Web Application Security & XSS Mitigation Lab

Source: Dev.to

Implementation

• Local PHP‑based web stack using VS Code + PHP built‑in server
• Two environments:
  • Vulnerable site (no input validation or encoding)
  • Secure site (defense‑in‑depth controls)
• Demonstrated both reflected and stored XSS attacks using real JavaScript payloads

Observability & Detection

• Pattern‑based input inspection to detect injections
• Server‑side logging of suspicious payloads to xss_log.txt
• Browser dev tools used to verify execution vs. prevention

Hardening & Prevention (DevOps Lens)

• Output encoding using htmlspecialchars()
• Input validation and sanitization
• Content Security Policy (CSP) to block inline and unauthorized scripts
• Layered controls to reduce blast radius even if one defense fails

Outcome

• Vulnerable site executed malicious scripts immediately
• Secure site blocked execution, logged attempts, and remained stable

DevOps Takeaway

This project reinforced how secure coding practices, observability, and policy‑based controls are critical to application reliability. From a DevOps perspective, XSS isn’t just a security bug—it’s an operational risk that can impact user trust, availability, and compliance.

https://youtu.be/yRzVNmUdgTQ