TypeScript's type system does not provide security guarantees — a SQL injection payload is still a valid string, and a malicious JWT still compiles. This comprehensive guide covers the major security vulnerabilities affecting modern TypeScript stacks: SQL and NoSQL injection (including ORM pitfalls with QueryBuilder and Raw()), prototype pollution, JWT algorithm confusion, timing attacks, React XSS via dangerouslySetInnerHTML and javascript: URLs, CSRF in SPAs, GraphQL introspection abuse and query complexity attacks, SSRF, unsafe serialization leading to RCE, and supply chain attacks including dependency confusion. It also covers where TypeScript genuinely helps — branded types for encoding trust boundaries — and closes with a practical security checklist for backend, frontend, and SSR contexts, emphasizing runtime validation at every trust boundary as the foundational defense.
Table of contents
TypeScript Is Not a Security BoundaryBackend Reality: HTTP Requests Arrive Before TypeSQL Injection Still Exists Inside ORM CodeThe Hidden ORM Trap: QueryBuilder and Raw()NoSQL Injection Is Still InjectionRuntime Validation Is Not Optional InfrastructurePrototype Pollution: The JavaScript Attack That Refuses to DieJWT Security: The Most Popular Misused Standard in Web DevelopmentSecrets Management: The Vulnerability Nobody Notices Until GitHub DoesTiming Attacks: When === Becomes a Security BugReact Security: Where Safe JSX Meets Unsafe RealityLess Obvious React Injection: URL ContextNext.js and SSR: Your Frontend Is Quietly Running Backend CodeCSRF: The Attack Many SPAs Assume They SolvedGraphQL Security: Flexibility Comes With Interesting Failure ModesSSRF: The Vulnerability That Turns Your Server Into an Internal Network ClientSupply Chain Attacks: Your Application Runs More Code Than Your Team WroteDependency ConfusionBranded Types: Where TypeScript Actually Helps SecurityPractical Security Checklist for Modern TypeScript ProjectsFinal ThoughtsSort: