Zano rolls blockchain back a month after Gateway Address exploit

Zano's development team has restarted the blockchain at block 3,833,000, the block immediately preceding Hard Fork 6, after discovering a vulnerability in the Gateway Addresses feature that permitted unauthorized ZANO and fUSD to be minted. The team said the rollback removes the unauthorized tokens but also invalidates roughly a month of legitimate transactions processed after that block height.

Gateway Addresses were introduced to simplify integrations for bridges, exchanges and payment services by allowing a single account-style balance rather than separate unspent transaction outputs (UTXOs). Zano confirmed the exploit stemmed from that feature, though it had not published a full post-mortem at the time of the report. The chain restart took place on Sunday, according to the project's blockchain explorer.

Because the rollback recreates chain state before the hard fork, any transactions included in the discarded month will no longer appear on the recovered Zano ledger. The team noted the restart cannot undo payments that have already been settled on other blockchains. Zano said it is working to quantify losses and will publish a reimbursement and claims process for those affected.

Project leadership framed the decision as necessary to prevent unlimited unauthorized token issuance, which would dilute holders and violate the intended fixed-supply promise. Zano's head of marketing and growth, Quinten van Welzen, acknowledged the action sacrifices a month of history and damages trust but said it restores the supply conditions users originally accepted and provides a path to rebuild. Zano launched in May 2019 as a privacy-focused layer-1 that supports private transactions and allows creation of custom tokens such as fUSD.