i am trying to exploit a vulnerability in a php script of the 'stop us' challenge of Wechall.net and I am not sure but I think I found the vulnerability, but now I don't know how to exploit it. I made some researches at PHP.net and I believe that a user can abort/close the connection and after that, the progress of the script terminates, because ignore_user_abort is not set, so after the 'domain' , in the script below, is purchased, the attacker can close the connection and the balance is not reduced. Here is the vulnerable code of that challenge: Vulnerable Code

How can I close/abort the connection at the specific time? (Race window)

2 Answers 2


In Chrome, you can simply press the ESC button to close/abort the connection. Look at the PHP code and you'll see when exactly you should press the ESC button.


I'd rather try to send multiple requests simultaneously. In the vulnerable code, it takes 10 seconds from the check (if you have enough money) till the paying process finishes. Another request arriving just in this timespan might enjoy "free shopping".

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