A significant blockchain shakeup has occurred with Monero (XMR), involving an 18-block reorganization. This unusual event has prompted blockchain analysts to express concerns about potential double-spending exploits on the Monero network.
Following the 18-block adjustment, Monero users are now being cautioned that the customary practice of awaiting 10 transaction confirmations before considering a transaction secure may no longer provide adequate protection.
⚠️The attack against Monero is back. Hours ago XMR experienced a 18 block reorg
If you accept XMR make sure to wait for more than the usual 10 confs pic.twitter.com/793j5WWXgZ
— OrangeFren.com (@OrangeFren) September 14, 2025
18-Block Reorganization Raises Double-Spending Fears for Monero
Monero (XMR) users are on alert after a notable 18-block chain reorganization impacted the network. Screenshots circulating on social media platform X confirm this unusual event, leading to fears that the cryptocurrency might be susceptible to double-spending attacks.
A blockchain reorganization takes place when two different versions of the blockchain emerge concurrently, and one chain ultimately supersedes the other. The transactions and blocks within the overtaken chain are then discarded.
In the case of Monero, new blocks are generally added every two minutes. Consequently, an 18-block reorganization essentially revises more than thirty minutes’ worth of transaction records.
While minor chain reorganizations affecting one or two blocks can naturally occur in proof-of-work blockchain systems, an 18-block event is decidedly uncommon. This suggests possible deliberate interference or a problematic concentration of mining resources.
Cosine, a security expert and founder of SlowMist, cautioned, that without proper attention to these block reorganizations from the Monero community, the persistent threat of double-spending remains. He highlighted that the potential for double-spending now exists, even if a single entity does not fully control 51% of the network’s hash rate.
Reports indicate that due to this incident, relying on the standard practice of waiting for 10 confirmations may not sufficiently protect against double-spending vulnerabilities.
Protecting Your Monero: Potential Safeguards
This is not the first time Monero has dealt with worries regarding mining influence. Back in August 2025, the Qubic project, a controversial mining initiative, reportedly secured a majority of the network’s hash power, as reported previously. At that point, major exchanges, including Kraken, temporarily halted Monero deposits because of the possibility of a 51% attack resulting in reorganizations and double-spending.
This recent 18-block reorganization seemingly confirms the validity of those prior concerns. Blockchain information reveals competing chains being formed by significant mining groups like monero.hashvault.pro and supportxmr.com, with blocks from smaller or less-known pools frequently being rejected.
This environment creates opportunities for malicious actors to substitute transactions or attempt double-spending through carefully planned chain reorganizations.
A user could send XMR, wait for the standard 10 confirmations, and then find their payment nullified if a deeper blockchain takes over the chain that included their transaction. In this case, the sender could effectively “double-spend” those coins elsewhere.
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