Update: Data from Coin.Dance and BitMEX Research confirms that the reorg was only 2 blocks deep. The orphaned blocks were 16MB and 13MB in size. This likely means that the reorg was unintentional and not an attack. Possible causes include poor network connectivity and/or block propagation.
According to Bitcoin Cash Fork Monitor, Bitcoin SV, one of two newly created cryptocurrencies resulting from last week's Bitcoin Cash hard fork, appears to be experiencing a block reorganization attack (reorg). A reorg attack could potentially delay or reverse transactions on a blockchain. Bitcoin SV's reorg appears to have happened on block 557301 — potentially invalidating every block mined after it. It is unclear whether this was an intentional attack or an accidental consensus split, which is common in small networks like Bitcoin SV. Some notable members of the Bitcoin Cash community believe this reorg attack was a "false flag" to prevent exchanges from accepting Bitcoin SV for deposit — avoiding a potential price dump of the cryptocurrency. As of the time of this writing, Bitcoin SV's blockchain is currently on block 557319.