Privacy-focused blockchain Monero suffered an 18-block reorganization on Sunday, which some analysts claim is the largest in the network’s history.

The reorg started at block height 3,499,659 and ended at 3,499,676, lasting about 43 minutes. 

It replaced 18 consecutive blocks, reversing 117 confirmed transactions, and raised significant security concerns about double-spending risks and network stability.

This story is an excerpt from the Unchained Daily newsletter.

The reorg was at the hands of mining pool Qubic, which employs a “selfish mining strategy,” where it deliberately withholds newly mined blocks instead of immediately broadcasting them to the Monero network to gain a higher share of mining rewards.

Qubic founder Sergey Ivancheglo, better known by the pseudonym Come From Beyond, claims that “not even a single Monero transaction was invalidated.”

Despite the network breach, Monero’s native token XMR rose about 7.4% following the reorg.