Web Security Basics: OWASP Top 10 for Developers (2026)
Web Security in 2026: The Stakes Are Higher Than Ever
Web application security vulnerabilities have real consequences: user data exposure, financial loss, regulatory penalties under GDPR and CCPA, and reputational damage that can end a startup. The OWASP Top 10 — the Open Web Application Security Project's list of the most critical web application security risks — provides a framework for understanding and addressing the most impactful vulnerability categories. Understanding these vulnerabilities and their mitigations is a baseline competency for any developer shipping to production in 2026.
Injection: SQL, NoSQL, Command
Injection attacks occur when untrusted data is sent to an interpreter as part of a command or query. SQL injection remains one of the most common and devastating vulnerabilities despite being fully preventable. The fix: never concatenate user input into SQL queries. Use parameterized queries or ORM methods that handle escaping. Django's ORM, SQLAlchemy, and all major ORMs are safe by default — raw SQL constructed with string formatting is not. The same principle applies to LDAP queries, OS commands, and XML parsers.
XSS: Cross-Site Scripting
XSS attacks inject malicious scripts into web pages viewed by other users. Stored XSS saves the payload in the database; reflected XSS returns the payload in the immediate response; DOM XSS manipulates client-side code. React and Vue escape content by default — using dangerouslySetInnerHTML in React or v-html in Vue bypasses escaping and requires explicit sanitization with DOMPurify. CSP (Content Security Policy) headers provide a defense-in-depth layer by restricting which scripts can execute on the page.
Broken Authentication
Broken authentication encompasses weak passwords, missing account lockout after failed attempts, exposed session tokens in URLs, and missing secure/httpOnly flags on session cookies. Mitigations: use established authentication libraries rather than rolling custom auth, enforce strong password requirements and support passkeys/WebAuthn, implement rate limiting on authentication endpoints (5 attempts before lockout), store session tokens in httpOnly SameSite=Strict cookies not localStorage, and rotate session tokens after privilege escalation.
IDOR and Access Control
Insecure Direct Object Reference (IDOR) allows attackers to access other users' data by manipulating identifiers in requests — changing /api/orders/123 to /api/orders/124 to access another user's order. Fix: validate that the authenticated user has permission to access each specific resource, not just that they're authenticated. Never rely on obscurity (using non-sequential UUIDs instead of integers) as the sole protection — implement explicit authorization checks. Django's object-level permissions or custom permission classes in DRF handle this cleanly. Download our security-hardened Django API template at proofmatcher.com.
Originally published at https://proofmatcher.com/blogs/web-security-owasp-top-10-2026