Ledger CTO Charles Guillemet pointed out today (12th) on social media platform X that the privacy-focused cryptocurrency Monero (XMR) seems to have suffered a 51% attack. (Background: Is Monero facing a decentralization crisis? Qubic aims to seize Monero's '51% hash power,' analysts: a wake-up call for all PoW) (Additional background: Monero developers' new project) Privacy chain Tari mainnet launched, $XTM mining opened, how to participate?) A shocking message has spread in the cryptocurrency world! Ledger CTO Charles Guillemet pointed out today (12th) on social media platform X that the privacy-focused cryptocurrency Monero (XMR) seems to have suffered a 51% attack. He stated that the Qubic platform, co-founded by IOTA co-founder Sergey Ivancheglo, has been secretly accumulating hash power for months, and now holds the majority hash power of the Monero network, triggering a significant blockchain reorganization this morning. This move allows Qubic to rewrite the Monero blockchain, implement double spending, and even censor any transaction, seriously threatening the decentralization of Monero: Monero (XMR) appears to have experienced a successful 51% attack. This privacy-focused blockchain, launched in 2014, is already banned from most major centralized exchanges. The Qubic mining pool has been accumulating hash power for months and now controls the majority of the network's hash power. A significant chain reorganization was detected this morning. With its current dominance, Qubic can rewrite the blockchain, enable double spending, and censor any transaction. The cost of maintaining this attack is estimated to reach 75 million dollars per day. While it may lead to massive profits, it has almost overnight destroyed confidence in the Monero network. Other miners are left with no motivation to continue mining since Qubic can easily isolate any competing blocks, effectively becoming the only miner. In fact, a chain worth 300 million dollars is taking over a chain worth 6 billion dollars. Monero's recovery options are limited, and a complete takeover is not just possible, but highly likely. Monero appears to be in the midst of a successful 51% attack. The privacy-focused blockchain, launched in 2014 and long targeted by governments and three-letter agencies, is already banned from most major centralized exchanges. The Qubic mining pool has been amassing hash power for… — Charles Guillemet (@P3b7_) August 12, 2025 In response to this news, well-known blockchain security company Slow Mist founder Yu Xian also retweeted Guillemet's post, stating that he has been paying attention to this matter for some time. He pointed out: "This 51% attack on Monero seems to have succeeded, but the cost is extremely high, and the economic benefits remain unclear." Yu Xian warned that the Qubic mining pool theoretically can rewrite the blockchain, implement double spending, or censor transactions; relevant platforms should closely monitor potential threats and remain vigilant. Image Source: Yu Xian The background of the Qubic hash power struggle The Qubic platform was founded by IOTA co-founder Sergey Ivancheglo and employs a 'useful proof of work' (uPoW) consensus mechanism, attempting to apply hash power to practical tasks. At the end of July, according to MiningPoolStats data, Qubic's share of the global Monero hash power surged from less than 2% on May 18 this year to over 27%, making it one of the largest mining pools for Monero. Sergey Ivancheglo publicly discussed this on social media platform X, stating that to demonstrate the capabilities of Qubic's 'useful proof of work' (uPoW) mechanism, he planned to seize over 51% of Monero's hash power from August 2 to August 31, 2025. Currently, Sergey Ivancheglo has retweeted related information on X, seemingly confirming the intention to carry out a 51% attack on Monero. XMR fell 8.8% Due to this news, as of the time of writing, Monero has dropped 8.8%, currently reported at 251 dollars, with a market cap of approximately 4.6 billion dollars. Related Reports On-chain detective warns: Suspected 330 million dollars in Bitcoin stolen and laundered for Monero, XMR surged 50% at one point Monero crowdfunding wallet hacked 'lost 2,675 XMR', community proposes disbanding core development team Monero enters an era of 0 inflation! Long-tail emission mechanism activated, block reward fixed at 0.6 XMR, with a 60% increase in a single month "Monero suspected to have suffered a 51% attack! Ledger CTO: Qubic holds the majority hash power, can rewrite XMR blockchain, implement double spending.." This article was first published on BlockTempo (the most influential blockchain news media).

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