Polygon PoS Deploys Private Hard Forks on Bor and Heimdall
Austin and Kyoto upgrades closed resource-exhaustion and consensus risks on Polygon PoS before public disclosure, with no mainnet impact observed.
Polygon PoS executed coordinated private hard forks on its Bor and Heimdall clients to address resource-exhaustion and consensus risks before any public disclosure or observed exploitation on mainnet.
What the patches addressed
The Austin fork on Bor v2.10.0 added a per-block gas bound for state-sync events and removed the unbounded TxDependency field. The Kyoto fork on Heimdall v0.11.0 capped nested protobuf.Any fields and added multiple hardening checks for checkpoints, milestones, and L1 events.
Both upgrades activated after validation on the Amoy testnet. Austin reached mainnet at block 91,949,700 and Kyoto at block 51,533,000. No mainnet disruption occurred and both forks were already active at the time of disclosure.
Open questions
Exact remaining unpatched surface after the listed fixes and any future coordinated disclosure timeline remain unknown.