Thank you for your response. I cannot see that PC would be infected (using AVAST, Microsoft Defender/Firewall with weekly scheduled scanning for viruses and malware). How could someone got knowledge about private keys? Was the reason that Core node (and wallet) had to be open for several weeks for it to be synchronized?

As the linked mining address cannot be changed for already pending mining assets, I can only hope to be quicker and to withdraw the mining deposit as soon as it comes to another address? Can I still use the same Core version to make new address (in order to make deposit/withdrawal from compromised to a new one) or is it better to download new version?

Hello!

In January I downloaded a new version of Bitcoin Core wallet from  https://bitcoincore.org/. After  waiting for almost 3 weeks to get node fully synchronised and to see the wallet's balance, I discovered that in the meantime on 11/02 all my assets that were stored in the Bitcoin Core (v0.20.1) were stolen to SegWit address bc1qz6k55y7z20azt596u80mtp0p53v9qnrj534t3k . I have never shared anything (seeds or private keys) regarding my BTC wallet address and thought that funds are save by using full node wallet.

How could this happen? What can I do, to still use this wallet to receive on it my pending mining that is still linked (and cannot be "un-linked" to the address from where the funds have been stolen?

Any suggestions would be much appreciated.