Web Application Security: A Comprehensive Developer Guide

Web application security is the discipline of protecting web-based applications from threats that exploit vulnerabilities in application code, configuration, and architecture. As organizations move critical business processes online, web applications have become the primary attack vector for data breaches, account takeover, and service disruption.

The web application attack surface spans multiple layers:

• Client-side: JavaScript executing in the browser, DOM manipulation, local storage, cookies, and cross-origin interactions
• Transport: HTTPS configuration, certificate validation, and man-in-the-middle protections
• Server-side: Input processing, authentication, authorization, session management, database queries, and system command execution
• API layer: REST and GraphQL endpoints, token management, rate limiting, and data exposure controls
• Dependencies: Third-party libraries, frameworks, and packages with known vulnerabilities

Modern web frameworks (React, Next.js, Django, Spring) provide built-in protections against some common vulnerabilities, but developers can bypass these protections through escape hatches, misconfiguration, or by using unsafe patterns that the framework does not cover. Security requires active verification at every layer, not passive reliance on framework defaults.

The OWASP Top 10 categorizes the most critical web application security risks. These vulnerabilities appear across all languages and frameworks:

Injection (OWASP A03)

Untrusted data sent to an interpreter as part of a command or query. SQL injection, XSS, command injection, and NoSQL injection all fall under this category. Injection remains the most exploited vulnerability class because every web application processes user input.

Broken Access Control (OWASP A01)

Users acting outside their intended permissions. This includes accessing other users' data by manipulating IDs, accessing admin functions without authorization, and missing function-level access checks.

Security Misconfiguration (OWASP A05)

Default credentials, unnecessary features enabled, verbose error messages exposing internals, missing security headers, and overly permissive CORS policies. Misconfiguration is the broadest category because it spans every component in the stack.

Cryptographic Failures (OWASP A02)

Sensitive data transmitted or stored without proper encryption. This includes HTTP instead of HTTPS, weak hashing algorithms for passwords (MD5, SHA-1), hardcoded secrets, and missing encryption for sensitive database fields.

Vulnerable Components (OWASP A06)

Using libraries and frameworks with known CVEs. A single vulnerable dependency can compromise the entire application. The Log4Shell vulnerability (CVE-2021-44228) demonstrated how one library can affect millions of applications.

HTTP security headers instruct the browser to enable protections that mitigate entire vulnerability classes:

• Content-Security-Policy (CSP): Controls which scripts, styles, and resources the browser can load. A strict CSP mitigates most XSS attacks by blocking inline scripts and restricting script sources.
• Strict-Transport-Security (HSTS): Forces HTTPS connections and prevents protocol downgrade attacks. Without HSTS, attackers on the network can intercept the initial HTTP request before the redirect to HTTPS.
• X-Frame-Options: Prevents clickjacking by controlling whether the page can be embedded in iframes. Set to DENY or SAMEORIGIN.
• X-Content-Type-Options: Prevents MIME type sniffing that can lead to script execution from non-script content types.

Session Management

Session security depends on proper cookie configuration:

• httpOnly: Prevents JavaScript access to session cookies, blocking XSS-based session theft
• secure: Ensures cookies are only sent over HTTPS connections
• sameSite: Controls cross-site cookie behavior. Strict or Lax prevents CSRF attacks at the browser level

Missing any of these attributes weakens the entire session security model. A cookie without httpOnly can be stolen by a single XSS vulnerability.

CodeSlick provides comprehensive web application security scanning with 294 checks across JavaScript, TypeScript, Python, Java, and Go:

• Injection detection: SQL injection, XSS (DOM, reflected, stored), command injection, NoSQL injection, SSRF, and path traversal across all supported languages
• Security header analysis: Flags missing CSP, HSTS, X-Frame-Options, and X-Content-Type-Options headers
• Cookie security: Detects cookies missing httpOnly, secure, and sameSite attributes
• API security: 5 dedicated checks for insecure HTTP, missing auth, API key exposure, CORS misconfiguration, and rate limiting gaps
• Dependency scanning: Identifies known-vulnerable packages in npm, pip, Maven, and Go modules

All scans complete in under 3 seconds with OWASP 2025 95% coverage, CWE classification, CVSS scoring, and AI-powered fix suggestions for every finding.