Important update: https://bitcointalk.org/index.php?topic=5034070.0If you are
currently running Bitcoin Core, then you must upgrade to 0.16.3 as soon as possible. You can download it from
bitcoin.org or
bitcoincore.org or via
BitTorrent, and as always, make sure that you
verify the download.
If you only occasionally run Bitcoin Core, then it is less urgent, though it would be best to upgrade as soon as convenient.
A bug was found which allows anyone capable of mining a sufficient-PoW block to crash Bitcoin Core nodes running versions 0.14.0 to 0.16.2.
Stored funds are not at risk.
Since most altcoins are based on Bitcoin Core, I would guess that many of them are also affected, though I don't have any specific info on that at this time. Also, Core derivatives such as Knots are affected and have their own updates.
Main release thread:
https://bitcointalk.org/index.php?topic=5032424.0
