A series of events unfolded over the weekend as a denial-of-service attack hit Litecoin, resulting in a 13-block chain reorganization that rewound approximately 32 minutes of network activity. The attack exploited a vulnerability in the Mimblewimble Extension Block (MWEB) protocol, which had been privately patched between March 19 and 26, but not publicly disclosed or mandated for all mining pools. This created a window of opportunity for attackers to target unpatched nodes, allowing invalid MWEB transactions to be processed before the network's longest valid chain corrected them.
The Litecoin Foundation has since released version 0.21.5.4, which includes important security updates, and has advised all users to upgrade. Researchers have raised concerns over the timeline of events, suggesting that the vulnerability was known and patched a month prior to the attack, but not publicly disclosed. The incident highlights the challenges faced by older proof-of-work networks like Litecoin in responding to security exploits and coordinating upgrades across independent mining pools.