The core vulnerability exists in two layers: 1) The API endpoint handler (post_validate_code) lacked authentication, allowing unauthorized access. 2) The validation logic (validate_code) used unsafe exec() with user-controlled input. The patches add auth to the endpoint but don't modify the underlying code execution mechanism, indicating validate_code remains the injection point when called without proper auth checks. Both functions would appear in exploitation stack traces - the endpoint handler from HTTP request processing, and validate_code during code execution.