The original title is: "4 Security Bugs I Found in My Own Auth System (And How I Fixed Them)"

Short summary

A developer shares four security vulnerabilities discovered in their own JWT-based authentication system and explains the fixes. The bugs include SQL injection via unparameterized queries, email enumeration through differentiated error messages, timing attacks from naive string comparison of passwords, and unrevocable refresh tokens. Each fix is demonstrated with concrete code using parameterized queries, generic error messages, bcrypt constant-time comparison, and Redis-backed token storage.

• •SQL injection fixed by switching to parameterized queries with PostgreSQL placeholders
• •Email enumeration prevented by returning identical 'Invalid credentials' error for all auth failures
• •Timing attacks mitigated by using bcrypt.compare for constant-time password verification
• •Refresh token revocation enabled by storing tokens in Redis with TTL instead of relying on stateless JWTs alone

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