NULS blockchain was hacked on December 23, 2019, losing 2M NULS tokens (~$480K) through exploitation of a signature verification vulnerability in NULS V2.2. Attackers compromised a NULS team account and transferred the funds. Of the stolen tokens, 548K NULS entered trading markets while 1.45M were frozen. NULS responded with an emergency hard fork at block 87,800 to permanently destroy the frozen tokens.

The well-known public chain NULS suffered a hacker attack and lost nearly $480,000 worth of NULS tokens. The SlowMist security team analyzed and found that the reason for the attack was that there was a loophole in the NULS transaction signature verification algorithm. The hacker bypassed the signature verification by using a carefully constructed transaction, transferred the tokens of the team account, and then some tokens were thrown into the market. , At present, major exchanges have suspended the deposit and withdrawal of NULS. After the attack, the official urgently checked the problem, carried out problem repair and code testing, and then released a new version of the program, and scheduled a hard fork at the height of 878000 (about noon on December 25th, Beijing time) to freeze other tokens that have not flowed into the market.