I am very interested to know if cryptocurrency wallets like Bitcoin Core, NEON, Electrum can ever be hacked ?
Wallets can be hacked only on one condition, if the hacker gets hold of some hole created by the owner/user of the wallet. This case is true for wallets that are truly decentralized like bitcoin. Some wallet's security feature may be so out of place that it will make the first case I pointed out to be a two-way thing, that is, even the software itself can be hacked.