Recently, the decentralized exchanged called EtherDelta had their DNS servers hacked. The exchange itself was not compromised, and as long as you were made aware of the hack and did not logon until the issue was resolved, you should be fine.

What did happen was that the hackers decided to create an identical looking website to Etherdelta's. Then by hacking Etherdelta's DNS servers, they could fool an individual's computer that was looking to access Etherdelta's exchange. The user's computer would instead be routed to the hacker's website that looks like Etherdelta. Their, the unsuspecting user would enter his credentials while the hacker was on the other end receiving this information. The hacker would now be able to logon on to the real Etherdelta exchange with the user's information and be able to drain the wallet of its coins.

Etherdelta has since addressed this issue and as of a few hours ago stated via their Twitter account that the system was back online. It seems that Etherdelta is now using Cloudflare's services to better secure their internet presence and make them stronger than ever. I have currently used the exchange to check my account, and everything is still there. Fortunately I do not keep much online for this very reason. I mostly store my coins/tokens in a hardware wallet such as the Ledger Wallet Nano S.