So today I ran into this one on the ETN Network. A huge amount of orphaned blocks. Time to explain what stale and orphaned blocks are on the chain.
At https://etnpool.net they temporarily saw a huge spike in hashrate what could have be a part of the cause of Orphaned blocks.
Stale blocks:
At any second, a block may be "solved." This means that everyone else in the world working on that block must stop, and restart their work. Continuing to work after that point is known as working on a "stale block" because it is old data, and old transactions.
My understanding is the term stale is much more commonly applied to shares when mining in a pool, so you're more likely to hear about stale shares than stale blocks. In this case, the pool probably wouldn't even bother checking whether the share actually solved a block or not.
Orphaned blocks:
Detached or Orphaned blocks are valid blocks which are not part of the main chain. They can occur naturally when two miners produce blocks at similar times or they can be caused by an attacker (with enough hashing power) attempting to reverse transactions.
My own understanding is that orphaned blocks are initially accepted by the majority of the network, but are later rejected when proof of a longer blockchain is received that doesn't include that particular block.
This means that a user could see a transaction as having one confirmation and then, if a longer blockchain was received that didn't include the transaction, it could change back to 0 confirmations
