The Bitcoin Core development team released an important update on September 18, Bitcoin Core 0.16.3, to fix a severe denial-of-service vulnerability.
The bug that was found would allow any miner on the Bitcoin network to bring down vulnerable Bitcoin nodes via duplicate input. This may affect all cryptocurrencies based on Bitcoin Core. The software is designed to provide Bitcoin wallets which thoroughly verify payments.
As advised in the release notes published by the Bitcoin Core developers, all nodes need to be upgraded to the new version as soon as possible by shutting them down and reinstalling using the platform-specific procedure.
The problem went by unnoticed, primarily because no one attempted to exploit it. Developers have successfully prevented this problem from escalating further.