Polygon Labs: Emergency client upgrade notification after the Austin and Kyoto hard forks

According to CryptoSlate, Polygon Labs issued an urgent notice that Polygon PoS nodes remaining on the old versions of Bor or Heimdall have lost consensus after the activation of the Austin and Kyoto hard forks and need to upgrade to catch up with the network progress. Austin was activated at mainnet block 91,949,700, requiring Bor v2.1.0 or above; Kyoto was activated at height 51,533,000, requiring Heimdall v0.11.0 or above.

Austin fixed two types of Bor resource exhaustion risks: L1 to L2 bridging state synchronization events not counted towards the gas limit could slow down block processing; the TxDependency field having no size limit could lead to peer node crashes. Kyoto addressed vulnerabilities such as deep nested message attacks, fee coin scanning, and checkpoint signature recovery. Both hard forks are pure binary upgrades, requiring no state migration, and non-forked nodes do not need to resynchronize. Operators of old clients should upgrade and restore synchronization under Polygon's guidance if necessary.