HiddenTear is the name of a ransomware family whose full source code was published on GitHub. This allowed attackers to download the source code and create their own ransomware variants that could be used to infect victims. As the original code was decryptable, this means all other ransomware created from the same code are decryptable as well. If you have been infected with a ‘HiddenTear’ Ransomware variant, you can use the following guide to decrypt files encrypted by this tool for free. In order to recover your encryption key, you need an encrypted file and its original unencrypted version.
Source: https://www.bleepingcomputer.com/ransomware/decryptor/how-to-decrypt-hiddentear-ransomware-variants/