The master decryption key that Kaseya used to unlock the files encrypted by a REvil ransomware attack on the company was leaked on the dark web. The key is of little use to other companies hit in the spate of attacks unleashed before the notorious ransomware group went dark on July 2. Researchers said they patched the decryptor binary with the annotated key from the thread and successfully decrypted a sandbox infected with the new REvil test sample upon changing the file extensions to universal_tool_xxx_yyy as seen in the screenshot.
Source: https://threatpost.com/kaseyas-master-key-to-revil-attack-leaked-online/168565/