Hackers found security weaknesses that allowed them to overdraw accounts with Flexcoin and Poloniex, two websites that facilitate bitcoin transactions, and exploited them to steal bitcoins from the two services. The attacks put Flexcoin out of business and cost Poloniex's users 12.3 percent of their bitcoins.
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News about Flexcoin
Flexcoin, a site that described itself as the "world's first bitcoin bank," has closed after it got hacked and all of the bitcoins it had placed in online storage were stolen, the site recently announced.