Bitcoin Cash reportedly suffered a 51% attack following its May 15 scheduled hardfork upgrade.
Following Bitcoin Cash’s hardfork upgrade, an attacker exploited a vulnerability in the update that added invalid transactions to the pool of unprocessed transactions (the Mempool). One source claims these were “poison” transactions that made it so miners were unable to participate in mining.
The exploit crippled the network for an hour and a half. The majority of miners were unable to participate in consensus, while those remaining were only able to mine mostly empty blocks.
Anouther source suggests that BTC.TOP opted to mine empty blocks to continue reaping mining rewards.