https://www.bleepingcomputer.com/news/security/muhstik-ransomware-victim-hacks-back-releases-decryption-keys/

A victim of the Muhstik Ransomware has hacked back against his attackers and released close to 3,000 decryption keys for victims along with a free decryptor to get their files back.

Since the end of September, an attacker has been hacking into publicly exposed QNAP NAS devices and encrypting the files on them. This ransomware has been named Muhstik based on the .muhstik extension appended to encrypted files.