Late Friday and Saturday, a series of events unfolded as a 13-block chain reorganization occurred on the Litecoin network, effectively rewinding 32 minutes of network activity. This reorganization was a response to a denial-of-service attack that exploited a vulnerability in the Mimblewimble Extension Block (MWEB) protocol, allowing invalid transactions to bypass nodes that had not been updated. The Litecoin Core v0.21.5.4 release was subsequently made available, advising all users to upgrade due to important security updates. According to the Litecoin Foundation, the bug was fully patched, and the network was operating normally by Sunday morning.

However, a review of the litecoin-project GitHub repository by prominent researchers, including security researcher bbsz, revealed that the consensus vulnerability had been privately patched between March 19 and March 26, roughly four weeks before the attack. This timeline indicates that the vulnerability was known and patched but not publicly disclosed or mandated for all mining pools, creating a window of opportunity for the attackers. The attackers appeared to be aware of which miners were running the patched code and which were still vulnerable, exploiting this knowledge to their advantage. Concerns were raised by Alex Shevchenko, CTO of NEAR Foundation's Aurora project, who pointed out that the denial-of-service attack and the MWEB bug were separate components, with the DoS designed to take patched mining nodes offline.

Blockchain data showed that the attacker had pre-funded a wallet 38 hours before the exploit, with plans to swap LTC for ETH on a decentralized exchange. The fact that the network automatically handled the 13-block reorganization once the DoS stopped suggests that enough hashrate was running updated code to eventually overpower the attack. This incident highlights the differences in how various networks respond to exploits, with newer chains often coordinating upgrades quickly and older proof-of-work networks like Litecoin and Bitcoin relying on independent mining pools to upgrade, creating potential windows of vulnerability.