  A good amount of effort has been dedicated to surveying and systematizing
Ethereum smart contract security bug classes. There is, however, a gap in
literature when it comes to surveying implementation-level security bugs that
commonly occur in basic PoW blockchain node implementations, discovered during
the first decade of Bitcoin's existence. This paper attempts to fill this void.
In particular, if software which participates in a network by validating and
generating new blocks is developed from scratch, WCGW - What Could Go Wrong?
  Ten broad bug type categories are listed and for each category, known
examples are linked. Blockchain, as designed by the Satoshi's paper is exciting
and introduces several novel bug classes which are interesting to security
researchers. The paper is aimed at security testers aiming to start out in
blockchain security reviews and blockchain developers as a reference on common
pitfalls.
