Late Friday and Saturday, a chain reorganization was performed on the Litecoin network to reverse the effects of a denial-of-service attack that exploited a vulnerability in the Mimblewimble Extension Block protocol. The attack, which occurred despite a private patch being implemented between March 19 and 26, allowed invalid transactions to be processed by nodes that had not been updated. However, the network's longest valid chain eventually corrected these transactions, and the Litecoin Core v0.21.5.4 release was issued to address the vulnerability.
According to security researchers, the timeline of the patch and the attack raises concerns about the coordination of security updates among mining pools. The attack has been mitigated, but the incident highlights the challenges faced by older proof-of-work networks in responding to security exploits.