A cryptographic hash function is a hash function that is most suitable for use in cryptography. It is a mathematical algorithm that maps data of arbitrary size to a bit string of a fixed size (a hash). This is designed to be a one-way function. The only way to recreate the input data is through brute-force search.
Old versions of WordPress is vulnerable to weak hashing. The server sets the newbloguser key to a string that can be directly derived from the user ID. This allows remote attackers to bypass intended access restrictions. In this attack, the modification of system files or information is most likely possible.