Coss is/was a pretty cool project with loads of options and exchange paying parts of their fees to HODLers who have COS token.
Now without any notice they closed trading/withdrawals for 3-4 weeks. Their Reddit got full of exit scam accusations and they changed mods there.
Worth to add there was connection to make interview for http://fuk.io with COSS team and they wasnt replying lately.
Hope this wont end as anything bad but at this point its good to notice this. Even though you cannot take out anything if you had there.
I personally had and was making some cash from COS token but looks like it may be game over. When exchanges get into problems on BTC spikes it gives a bad feeling.
Top20 From Time They Worked

Worth to note they were an exchange that doesnt need documents to trade. If you look for other places that work and are daily verified by me and others from community here is few:
For x50-x100 leverage trading you have BitMex or BaseFX or ByBit
Anf here are huge cryptocurrency pair exchanges:
- Binance - top1 exchange in the world with best volumes and promotions
- KuCoin - i would call it younger brother of Binance with many NEO and ETH pairs
- BiBox - amazing China exchange, similar to other two above with different coins
- BitMax - crazy overlooked by people china exchange with loads of good options
- BitForex - currently top volume exchange for USDT pairs, really overlooked
- Coinex - ETH BCH BTC EOS pairs