Negative Bitcoin Balance

Question

I was playing around with bitcoin and I discovered an address that appears to have a negative balance on the blockchain.

The details of this address are below. At the time of writing the blockchain states the balance in the account is -0.00199614 BTC.

https://blockchain.info/address/12AKRNHpFhDSBDD9rSn74VAzZSL3774PxQ

Does anyone know how a negative balance is possible?

Details:

Bitcoin Address:
12AKRNHpFhDSBDD9rSn74VAzZSL3774PxQ

Public Key: 04FDF4907810A9F5D9462A1AE09FEEE5AB205D32798B0FFCC379442021F84C5BBFC891EB16B0FAEF4BEF99BA6D522FB85470A20DF730808E583778AA35C7AF98F5

Private Key:
6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b

Answer 1

It has a Negative Balance of -0.00199614 BTC, but it also has an unconfirmed transaction for the same amount. The transaction is from 2015.

That report page is showing unconfirmed transactions as well as confirmed. Presumably, that transaction will never get confirmed, because it would send the balance negative.

Answer 2

The website shows two transactions spending the same transaction output. Such a construct of two conflicting transactions is referred to as a "doublespend". Only one of the two transactions can ever be confirmed, at which point the other becomes invalid.

While I can see why it may be interesting to continue to show the invalid unconfirmed transaction, it is nonsensical to continue using it to calculate the final balance of the address. Frankly, I'd consider it a bug in blockchain.info.