Although this has not happen to our exchange where we put our funds for a long time, this should prove that its not safe to be there for months or years, you have to secure your money, or tokens/coins to your hardware wallet, or electrum wallet etc since you have full control unlike CEX.
Earlier there is a news that Coinex have been hack, where the hacker transfer and drain the wallet, with ETH, Polygon, Tron etc, i think this is the first time this exchange has been hack, i say i have coins there but no value, but if you have lots of eth and others thats is a major concern, since we don't know if they can refund the loses.
so to be safe store your bitcoin and other coins to safe wallet, like hardware wallet etc.
this is the link of the news :
https://cointelegraph.com/news/coinex-crypto-exchange-suspected-hacked-crypto-movedFirst, you need to edit your post, so many errors and the link to your source is not in clickable format as did in my quoted post. Again, you added that it didn't happen to "our", the 'our exchange', do you have an exchange or you are making your report in active voice?
There is nothing like the first time, a crime is a crime and that is not supposed to happen in the first place, don't leave your coins on any exchange, it is as simple as that. You should avoid centralized exchange like a plaque, they are not to be hack and if other centralized exchanges continue to operate like this, expect more hacks from the future, it is unavoidable but you can be part of the people who don't want use such kind of exchanges, always remember not your keys not your coins.