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The delayed implementation of a bitcoin core update by a small number of the network's miners resulted in the addition of invalid transaction blocks to the bitcoin blockchain this weekend.
The result was a fork in the network that created two versions of the bitcoin blockchain, which continued for six blocks on 4th July. An additional three invalid blocks were added to the blockchain in a repeat of the issue the following day.
As a result, core developers issued a warning on Bitcoin.org requesting that wallet providers place increased scrutiny on incoming transactions due to the risk that funds could be double spent as a result of the discrepancy between chains.
The result was a fork in the network that created two versions of the bitcoin blockchain, which continued for six blocks on 4th July. An additional three invalid blocks were added to the blockchain in a repeat of the issue the following day.
As a result, core developers issued a warning on Bitcoin.org requesting that wallet providers place increased scrutiny on incoming transactions due to the risk that funds could be double spent as a result of the discrepancy between chains.
Full story: http://www.coindesk.com/double-spending-risk-bitcoin-network-fork/