OKEx is an exchange right? So why would anyone be surprised if we see some huge movement?  You can follow everything here,

(https://twitter.com/whale_alert?lang=en)

OKEx, Huobi and Binance was moving tons of crypto's like every 3 hours so unlikely that this is a hacked, just the usual thingy top exchanges are doing today. Shifting their funds to wallets that are secure and safe. Nothing to be alarm here.