On December 6-7, 2017, NiceHash's payment wallet was compromised after attackers obtained employee credentials via phishing. The attacker accessed the wallet and stole 4,700+ BTC (~$64M). NiceHash eventually repaid all affected users by December 16, 2020.

Nicehash appears to have shuttered their website with a notice saying “a security breach involving NiceHash website” and “our payment system was compromised and the contents of the NiceHash Bitcoin wallet have been stolen”.