Frontrunning

Transactions are not instantaneously added to the blockchain. First, they are publicly transmitted to the nodes in the network and added to a pool of pending transactions. Later, they are added to a block and official become part of the distributed ledger

Priority is often given to transactions with a higher fee

This enables frontrunning attacks. After observing a transaction, an attacker can create one with a higher fee. This malicious transaction will likely be processed first

Frontrunning attacks can be used for a variety of purposes, like making a profit or winning a contest