The cryptocurrency world has been shaken by claims from Qubic, a project led by IOTA co-founder Sergey Ivancheglo, that it has allegedly seized majority control of the Monero blockchain’s hashrate. According to the team, this milestone was reached on August 11, 2025, after a focused push that lasted several weeks. The development has opened up concerns over Monero’s network security and the vulnerability of mid-cap Proof-of-Work blockchains to incentive-driven takeovers.
How Has The Monero Situation Played Out?
According to the Qubic team, the attack was carried out using a “useful proof‑of‑work” (uPoW or UPoW) model. Miners channel their CPU mining power toward Monero; Qubic then converts the mined XMR into USDT to buy and burn QUBIC tokens or reward its own validators. This economic design drew a substantial portion of the Monero mining power away from other pools, escalating from under 2% in May and culminating in the claimed 51% threshold by August. Qubic describes this as a strategic experiment not intended to destroy Monero but to test how incentives can be used to shift control over a network.
According to reports and mentions on the social media platform X, there was indeed a six-block reorganization on the Monero blockchain, which showed that Qubic does control a large enough hashrate.
If Qubic succeeded in gaining and sustaining majority control (over 50%) of the blockchain’s hashrate, the implications could be severe. In such a scenario, Qubic could potentially censor transactions, perform double-spends, and reorganize blocks at will. Such power would allow them to reverse confirmed transactions and undermine the blockchain’s integrity.
What Have Experts Said?
In response, the Monero developer community noted that chain reorganizations alone don’t confirm a true 51% attack. Luke Parker (lead dev at SeraiDEX) stated that a six‑block‑deep network reorg with block orphaning does not mean a 51% attack was successful. However, it does mean a mining group with a high amount of hashrate got lucky.
The CTO of Ledger, Charles Guillemet, also raised alarms regarding the incident. Guillemet warned that sustaining such a dominance could cost $75 million per day in equipment and operations, and that even that might compromise confidence in Monero nearly instantly.
Indeed, many in the Monero community are skeptical that Qubic truly sustained such control. According to a post by blockchain engineer Leonardo Faoro, which was also reposted on the social media platform X by Monero founder Riccardo Spagni, miners don’t need a full 51% hashrate to trigger reorgs. They only require about 35% of the hashrate, along with fortunate timing.
Monero’s market performance quickly reflected the unease in the hours following Qubic’s claim of majority control. This unease saw its price fall to as low as $245. At the time of writing, Monero is trading at $247, down by 5.3% and 15.2% in the past 24 hours and seven days, respectively.
Qubic’s native token, on the other hand, experienced the opposite trajectory. At the time of writing, QUBIC is up by 20.5% in the past 24 hours.
Featured image from iStock, chart from Tradingview.com
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