Slow Mist: Acala’s liquidity pool rewards were amplified due to incorrect settings on the chain

Slow Mist said that Acala called update_dex_saving_rewards at 6:23:12 on August 14, 2022, Beijing time to modify the reward multiplier of the aUSD pool to 500000000000000000. The accumulate_dex_saving function will be called in the hook function on_initialize of the block. In the function, the total reward of the pool is multiplied by dex_saving_reward_rate by dex_saving_reward_base. Since the dex_saving_reward_rate has been enlarged in the previous step, the reward of the pool has also been enlarged. In the end, the user received the wrong reward, which led to abnormal issuance of aUSD.