A blockchain is public ledger of transactions that is distributed among all participants in a market or system. Each transaction that happens within a market or system must be verified by a strong majority of participants. It's very difficult to falsify transactions in a blockchain because each transaction generates a strong cryptographic signature.
We all have our areas of interest -- make that obsession -- and when something related to them crops up online, we can be instantly transformed into monster click machines. The problem here: Many of those clicks can either lead to your victimization or becoming an unwitting co-conspirator in cybercrime.
First, don't panic. This is a serious problem but you need to put it into perspective. While there is clearly a vulnerability, there are so far no reports of the flaw being exploited. And even though this flaw has been around for the past two years, almost all the major sites have fixed it -- in some cases, in the last few days.