Which chain rolled back after exploit?

TLDR

Flow (FLOW) is the chain that moved to roll back after an exploit, then reversed course and avoided a full reorganization per a community update in late December Flow scrapped rollback plan.

1. The initial rollback proposal faced backlash and was replaced by a restart from the last sealed block with no reorg restart from last sealed block.
2. The exploit was about $3.9 million tied to an execution-layer vulnerability exploit size and details.
3. Recovery steps include restricting accounts, destroying fraudulent tokens, and rebalancing affected pools using foundation funds targeted recovery plan.

Deep Dive

1. Flow Incident

Flow halted after an execution-layer exploit around Dec 27 that siphoned roughly $3.9 million, with partners highlighting bridge and balance risks if the ledger were reversed incident overview. The initial idea was a rollback to a pre-attack checkpoint, which raised concerns about doubled balances and forced resubmissions across bridges and exchanges partner backlash and risks.

2. Recovery Plan

After pushback, Flow confirmed there would be no chain reorganization. Instead, the network would restart from the last sealed block and pursue targeted remediation (restricting accounts tied to illicit tokens, burning fraudulent assets, and rebalancing pools) no rollback confirmation. This approach aimed to preserve legitimate transaction history and minimize disruption to bridges and custodians plan specifics.

3. Why Rollback Matters

Reversing confirmed blocks undermines decentralization and creates uncertainty for users, bridges, and venues that acted honestly during the affected window decentralization concerns. Legal and technical voices argued rollback would externalize losses to partners by creating unbacked assets, favoring targeted fixes over history rewrites expert critique.

Conclusion

Flow considered and then abandoned a chain rollback, opting for a targeted recovery that preserves history and reduces harm to bridges and users. The episode highlights the trade-off between rapid intervention and blockchain immutability, with targeted fixes emerging as the more practical path under multi-venue constraints.