On Wednesday evening (UTC-time), a bug was found in the implementation of the ZKsync sequencer’s virtual machine that led to an unprovable batch being generated on Abstract. This led to a delay in finalization and withdrawals from the chain while the incident was being resolved. The sequencer VM has now been patched, and the fix has been rolled out to all chains in the Elastic Network.
An emergency protocol upgrade was prepared and deployed to finalize the previously unproved batch. The Emergency Upgrade was approved by Guardians, the ZKsync Security Council, and the ZKsync Foundation. The ZKsync Security Council has manually validated the batch that originally contained an issue.
No user funds were ever at risk and transactions were still processed normally during the incident.
A full incident report will follow.