I had hear some people said that thay can recorvery passphrase wallet.dat with open wallet.dat by hex editor.
it's real ?
Thank
The wallet.dat file uses DB format, so if you know the DB format you can see where the encrypted password is stored.
You cannot see the passphrase, but you can extract the string that is the encrypted form of the password and need to execute
some decoding on it before it becomes the passphrase.
So the claim is partly true, but most likely they are just trying to scam you to get into your wallet.
The thing you want to do is use bitcoin2john.py from the John the Ripper or Magnum Ripper github repo and with that string (which is a hash of the password) use various software to try to find your passphrase.
The most common is Hashcat and you can ask around at hashcat.org to find out how to use it most effectively.