What common mistake do developers make with Authorization failures, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with Authorization failures, why does the mistake cause problems, and what is the safer approach? One recurring problem with authorization failures is applying it without understanding the boundary it protects. Testing only the happy path and never verifying that an unauthenticated or unauthorized request is rejected. In addition, Tests should verify both allowed and denied actions so permissions do not regress silently. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.