Does WordPress validate inputs to all functions? (such as get_user_meta and insert_user_meta)

You have to do a lot by yourself. But you also have to check the core code by yourself to see if the current function you’re using is validating it and in which way.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)