A new version of the Petya disc-encrypting ransomware has been released that fixes a bug that previously caused some weakness in its encryption algorithm. According to Hasherezade, a security analyst for Malwarebytes, prior versions of the Petya ransomware were not properly implementing the Salsa20 encryption algorithm, which was used by the ransomware to encrypt the drive and for verifying that a correct ransom key was entered.
With this new version, the Petya developer's implementation of the Salsa20 algorithm has been fixed, which removes the previously exploitable weaknesses.