Hi,

I created a new receiving address yesterday in my local bitcoin-qt wallet, and received some BTC from an exchange.

Today I have sent 10 BTC to another exchange, which I can see in my history, and as pending on the exchange... but, when I check the transaction ID for this send, in addition to the 10 sent to my exchange wallet address, it looks like another 5 (4.9999774) has been sent to another address that I do not recognise....  and of course this send does not show up in my bitcoin-qt history.

Is this potentially a malicious double spend attempt? How do I fix it?

As an aside, the 10 was sent with the minimum fee by accident, which is why I've been watching the transaction fairly closely to see if I need to take measures to fix it...  but the extra 5 is concerning me more at the moment.

Details:

The receiving address in my local wallet:

https://live.blockcypher.com/btc/address/1GpotiZtcJcD8rcPrpuMfXvPD5GEPzRRJp/

Transaction ID for 10 BTC sent today:

https://live.blockcypher.com/btc/tx/884b508555942d9e7cc6694da905ccb99eb1098a3ccc5edca5cb1c55d2e557b0/