According to CoinMeta, Polygon Labs issued a notice regarding security reviews and an emergency client upgrade, stating that after the completion of the two major hard fork upgrades Austin and Kyoto in August, nodes Polygon PoS which were still running with the old version of binary files had deviated from the main chain's consensus rules (canonical consensus). Node operators are required to upgrade and resynchronize their systems. Specifically, the consensus layer client Heimdall activated the Kyoto upgrade at block height 51,533,000 on August 18 (with an upgrade needed to v0.11.0), which mainly fixed issues related to the abuse of nested messages, fee currency scanning, and edge cases with checkpoints.