Zano bug forces blockchain to erase a day’s transactions

The Zano blockchain experienced unintended token inflation after a flaw in transaction validation allowed extra coins to enter circulation. The core development team removed about 24 hours of blocks and rebuilt the ledger from the last confirmed good block to restore the intended money supply.

The team detected the problem after observing unusual balances and transaction patterns on the network. Investigators traced the issue to a validation error that was exploitable during a short window. Developers invalidated the affected blocks and reconstructed the chain without the transactions that had created the extra tokens.

A patched node client was published and node operators were instructed to upgrade and resynchronize to the corrected chain. Full-node operators reported they needed to download and validate the rebuilt chain from peers running the patched software to restore consistent ledger copies.

Users whose transactions were confirmed during the erased period lost those confirmations on the repaired chain. Wallet providers and custodial services were asked to notify customers that transactions within the removed window would no longer appear on the ledger and that affected payments might need to be rebroadcast after upgrading software. Some exchanges temporarily paused deposits and withdrawals while they verified balances.

Third-party wallet operators said they were coordinating with the core team to update clients and assist users in restoring valid funds. No central refunds were issued; the correction returned the ledger to a state that excludes the improperly minted coins.

Zano is a smaller, privacy-focused network maintained by independent community operators. The rollback required coordination across those independent nodes so the repaired chain could achieve consensus.

In a statement, the Zano development group wrote, “We have identified and removed the inflationary transactions and published a patched release. Node operators should upgrade and resynchronize to the corrected chain to ensure consistent balances.” The team added it will conduct a full audit of recent protocol changes and publish a post-mortem once immediate recovery work is complete.