Bitcoin Core 0.9.0 was made available yesterday that included new features as well as security updates. The software running the Bitcoin network was updated to resolve the transaction malleability issue that took down popular exchange Mt. Gox. The issue was addressed by tightening transaction rules preventing mutated transactions from being relayed or mined. Bug fixes also addressed incorrect balances being reported for mutated transactions, among other fixes, also addressed Bug fixes. MtGox’s demise was a perfect storm of software issues and policy failures that caused the Japanese company to lose hundreds of millions of dollars.
Source: https://threatpost.com/bitcoin-transaction-malleability-flaw-resolved/104926/