In August 2025, the crypto world was shaken by news of a 51% attack on the XMR (Monero) network by the Qubic project, sparking widespread public attention and analytical discussions.
Understanding 51% Attack
In the blockchain PoW consensus mechanism, network security depends on the honest work of the majority of the hash rate. If one party controls over 50% of the hash rate, it can conduct double-spend attacks and block reorganization, known as a 51% attack. Such events severely undermine blockchain decentralization and security.
Technical Analysis of the Attack
Rumors of an impending attack on XMR by Qubic pools began circulating in July 2025. On August 12, 2025, SlowMist confirmed a reorganization of the XMR blockchain by 6 blocks. Qubic employed a 'selfish mining' strategy, secretly mining new blocks, which forced other miners to work on an old chain and waste their efforts. This data confirmed Qubic's dominance over XMR's hash rate, enabling control over the block consensus mechanism.
Market Reaction and Consequences
Following news of the attack, XMR's market cap fell from $6 billion to $4.6 billion. Reports of longer transaction confirmation times led to a trust crisis in the community as users became concerned about network safety. Qubic also faced criticism for violating Monero's decentralization ethos despite their intentions.
The 51% attack on XMR reflects economic vulnerabilities in PoW security and demonstrates Qubic's unique computation model. For XMR, this poses both a challenge and an opportunity, demanding technical upgrades to maintain its leadership in privacy coins.
