Web - Server

Hey Rooters,
i having problems solving this challenge.
i tried very hard, i tried and analysed every single request and the internet, i used SQLMAP with every single tamper
i made some new requests
BUT without any result i can’t understand how that filter works
please any one can give me un petit hint :D
PS: I’ve been working on this challenge for about a month
thanks in advance

Hello mate,

am stuck in this too. If you have figured it out already, could you help out a bit.

Thanks