Proof-of-Stake: What if a bad enactor is chosen by random? My understanding of proof-of-stake is the following: 
The node that mines the next block is chosen, randomly in proportion to the amount of nodes they have in the network (ex. person who who owns 5% of all the tokens in the ecosystem has a 5% chance of being selected to mine the next block)

The block gets broadcasted throughout the network.

However, based on this principle of randomness, what if a bad enactor is chosen by chance.

What if a person wants to submit a block w/ fraudulent transactions (ex. instead of Bob sending Alice 1 cryptotoken, the fraudster changes up the transaction to make Bob send Alice 100 cryptotokens - assuming Bob owns 100+ cryptotokens)?

Thanks!
What if a person wants to submit a block w/ fraudulent transactions (ex. instead of Bob sending Alice 1 cryptotoken, the fraudster changes up the transaction to make Bob send Alice 100 cryptotokens - assuming Bob owns 100+ cryptotokens)?


In PoS, block validators lock certain amount of the network tokens into a deposit using a smart contract that designates them as validators. You cannot simply change the output as the signature used to verify 2 cryptokens being sent will not be valid if that number is changed to 100. Thus this transaction would be invalid according to the protocol. If the network determines that the validator has misbehaved then the entire deposit (or in some cases portion of the deposit depending on protocols on different chains) gets slashed. To go into exact technical details as to how it happens you can see Ethereum PoS FAQs here.