Security Best Practices

Atomic decision guides for building secure web applications across all languages and frameworks.

I need to...

I need to...	Guide	Summary
Understand the security mindset and defense principles	Security Mindset Overview	Every developer must adopt a security-first mindset from day one. Security is not a feature you add later — it's a fundamental requirement woven into every design decision, code commit, and deployment.
Know the most critical web vulnerabilities	OWASP Top 10	The OWASP Top 10 is the industry-standard baseline for web application security. Use this as your minimum security checklist — if your application is vulnerable to any Top 10 item, you have critical work to do.
Validate user input safely	Input Validation	Validate ALL input from untrusted sources: HTTP requests (parameters, headers, body), file uploads, API calls, database reads (yes, even database — consider SQL injection into another app), message queues, external APIs, environment…
Escape output correctly for different contexts	Output Encoding and Escaping	Escape ALL output that includes untrusted data before rendering in HTML, JavaScript, CSS, URLs, SQL queries, OS commands, or any interpreter context. Different contexts require different escaping rules.
Prevent cross-site scripting attacks	Cross-Site Scripting (XSS)	Understand XSS attack vectors whenever your application displays user-generated content, accepts URL parameters, or renders data from any untrusted source.
Implement XSS prevention patterns	XSS Prevention Patterns	Implement these defense-in-depth XSS protections in addition to (not instead of) input validation and output encoding.
Prevent SQL injection	SQL Injection Prevention	EVERY database query that includes any untrusted data — user input, URL parameters, cookies, HTTP headers, data from external APIs, even data read from your own database (defense in depth).
Protect against CSRF attacks	CSRF Prevention	Protect ALL state-changing operations: POST/PUT/DELETE requests, password changes, money transfers, profile updates, admin actions. GET requests should NEVER change state (by design, GET = read-only).
Implement secure authentication	Authentication Best Practices	Every system that identifies users needs secure authentication. This covers password-based authentication, multi-factor authentication, session management, and modern authentication protocols.
Design proper authorization systems	Authorization and Access Control	Every operation that accesses resources must check authorization — reading data, modifying data, deleting data, accessing admin features. Authentication answers "who are you?", authorization answers "what can you do?"
Protect sensitive data	Sensitive Data Protection	Protecting Personally Identifiable Information (PII), payment card data, health records, authentication credentials, business secrets, and any data that would cause harm if exposed.
Configure security headers	Security Headers	Configure security headers on ALL HTTP responses. Headers provide defense-in-depth against XSS, clickjacking, MIME sniffing, and other attacks.
Secure my APIs	API Security	Every API endpoint — REST, GraphQL, gRPC, webhooks — requires security controls. APIs are a prime attack vector: programmatic access, often less monitored than web UIs, frequently exposed to the internet.
Handle file uploads safely	File Upload Security	Any feature that accepts files from users — profile pictures, document uploads, file sharing, import features, email attachments. File uploads are extremely dangerous: remote code execution, stored XSS, DoS, malware distribution.
Manage dependencies securely	Dependency Security	Every project uses third-party dependencies — npm packages, PyPI libraries, Maven artifacts, gems, Go modules. Supply chain attacks are the fastest-growing threat in 2025.
Implement secure logging	Logging and Monitoring	Security logging and monitoring are MANDATORY for every application. A09:2021 Security Logging and Monitoring Failures — insufficient logging allows breaches to go undetected for months.
Understand cryptography basics	Cryptography Basics	Cryptography protects data confidentiality (encryption), integrity (hashing), and authenticity (signatures). Use for sensitive data at rest and in transit, password storage, message authentication, and digital signatures.
Integrate security into development	Secure Development Lifecycle	Integrate security into every phase of software development — from requirements gathering to deployment and maintenance. Security is not a gate at the end; it's woven throughout the entire process.
Avoid common security mistakes	Common Security Anti-Patterns	Learn from others' mistakes. These anti-patterns represent the most common security failures that lead to breaches.
Quick security checklist	Security Checklist	Use this checklist for security code reviews, deployment readiness assessments, and security audits. This is a quick reference distilling all sections into actionable items.
Find security resources and tools	Code Reference Map
Find sources and maintenance info	Sources and Maintenance Manifest	Web sources, code sources, and version history for the security best practices guide.