I wrote an article about this pending publication so I can't link you just yet. Bitcoin is mostly safe. Transactions in the pending pool can be compromised but

I wrote an article about this pending publication so I can't link you just yet. Bitcoin is mostly safe. Transactions in the pending pool can be compromised but quantum computers would need to perform logical operations at around 660 MHz. Confirmed transactions and unspent transactions are completely safe. The earliest quantum computers won't be fast enough to perform this attack. The problem is easily remedied by hard forking to replace ECDSA with a different public key system. There will be a lot of advanced warning. I'm not sure on Ether.