Qubic has restarted its blockchain after an attacker stole approximately 2.94 trillion QU tokens from 1,404 wallets in less than two hours, with the cryptocurrency valued at nearly $1.3 million.
The network was shut down on Oct. 18 after validators, known as Computors, halted transactions at tick 85,371,949 to prevent further losses. Transaction processing resumed by the evening of Oct. 19.
On Oct. 20, Qubic said its validators had approved a recovery plan, launched a claims portal and started making payments to victims whose claims had been verified.
The incident did not involve a breach of Qubic’s blockchain itself. Instead, the attacker exploited weaknesses in the recovery seeds generated by some older versions of Qubic’s wallet software.
Recovery seeds are secret strings of characters that provide access to cryptocurrency wallets. Qubic said an insecure random-number generator used in certain wallet software made some of those seeds predictable, potentially allowing attackers to reconstruct them and access funds without knowing the wallet owner’s password.
The affected wallets included those created through browsers on iPhones and iPads, Safari on Macs, and older versions of Qubic’s iOS application.
Qubic said the vulnerability was fixed in wallet version 4.26.4, released around Oct. 19, when the weak generator was replaced with a more secure system.
However, installing the update does not make an old recovery seed safe. Users who created wallets with the affected software must create a completely new wallet and transfer their funds. Opening an old wallet on another device does not resolve the problem.
The attacker was unable to remove all of the stolen tokens after the network was suspended. About 87.1% of the funds remained trapped on the blockchain, while cryptocurrency exchange MEXC froze an account containing the remaining 12.9%.
Qubic later moved the affected on-chain funds into protected escrow. That allowed its validators to begin returning cryptocurrency to owners whose claims had been confirmed.
Victims can apply through Qubic’s official recovery portal until May 1, 2027. Applications must include the affected wallet identity, a newly created destination wallet, a signed message proving ownership and supporting evidence.
Successful claims will be subject to a seven-day dispute period before payments are made. Recovery of the funds held by MEXC will depend on the exchange and any law-enforcement proceedings.
Qubic has warned users that genuine recovery assistance will never ask them to provide a wallet seed or pay a fee.
Although the blockchain is operating again, the theft highlights a separate security risk for cryptocurrency users: a network can remain uncompromised while weaknesses in the software used to access wallets expose funds to attackers.
