The daemon does not fully validate a blockchain that it loads from a file. This is certainly not a good thing. We will ultimately support a bootstrap format that is validated like Bitcoin does, but that functionality doesn't exist yet.
So downloaded blockchains should be used with care, only from a trusted source.
Ah ok, with that being the case I can see why a downloaded blockchain could be problematic if crafted maliciously. As people have no reason to trust me I will share the tricks I used to get my win x64 blockchain synced and updated. As I said in my edited post above:
If anyone wants to sync themselves due to the chance of a dodgy blockchain (mine isn't but I can understand the concerns - see smooth's post below), download the blockchain from the OP and then start bitmonerod with the flag "--add-priority-node 88.151.101.22:18080". That will preferentially try to sync to a known good node (thanks to hegemoOn and his pool [
monero.coolmining.club] for that). It's how I got my chain synced to the right fork. You can still end up on the wrong fork but this gives you a better chance.
Also, you can 'save' your blockchain in bitmonerod at around block 202000, so that way if you end up on the wrong fork just close bitmonerod without saving and try again.
