Hello!
Actually this is my coinbase address ► 15zLFJqBvfZ2F2hxKp1Ljx16vktUvoZpT1 and in blockchain.info it was showing that Warning! this bitcoin address contains transactions which may be double spends. You should be extremely careful when trusting any transactions to or from this address. untill yesterday i didn't saw this phrase. But i never did any double spent, unfortunately coinbase doesn't allows to and i don't know how to do too. But why should it shows the warning?
What should i do now?
My best guess is that its due to the recent malleability attack[1]. Just ask coinbase to rescan your wallet if they show a wrong balance, there is nothing else you can do at the moment. There is also nothing to worry about, all this will do is confuse people. Which is bad enough, but at least nothing is lost.
[1]
https://bitcointalk.org/index.php?topic=1198032.0;topicseen