# TypeScript Unsafe Type Guard

- ID: typescript-unsafe-type-guard
- Severity: HIGH
- CWE: CWE-704 (CWE-704)
- Languages: TypeScript
- Frameworks: typescript

## Description

Type guards that always return true or use assertions without validation create
type confusion, allowing untrusted data to bypass security checks.

## Detection Message

Type guard '{function}' uses 'is' predicate but lacks proper runtime validation. This creates type confusion vulnerabilities.

## Remediation

Implement proper runtime validation in type guards.

```typescript
function isUser(obj: unknown): obj is User {
  if (typeof obj !== 'object' || obj === null) {
    return false;
  }
  const u = obj as Record<string, unknown>;
  return (
    typeof u.id === 'number' &&
    typeof u.email === 'string'
  );
}
```

Learn more: https://shoulder.dev/learn/typescript/cwe-704/unsafe-type-guard

## Documentation

[object Object]

## Related Rules

- **tRPC Type Safety Bypass with Any** [MEDIUM]: 
- **TypeScript Unconstrained Generic Type Parameters** [MEDIUM]: 
- **TypeScript Strict Mode Disabled** [HIGH]: 
- **Unsafe 'any' Type in Security-Sensitive Context** [HIGH]: