user18196: I know the coinbase transaction's input is usually just has a dummy scriptSig, but what if a miner used it to spend an UTXO? Would it be verified as an actual spend, or would the block be rejected?

user21052: It would be rejected.  The coinbase input must use a very specific previous outpoint: 0x0000000000000000000000000000000000000000000000000000000000000000ffffffff. This prevents it from referring to an actual previous outpoint.

18196: <p>I know the coinbase transaction's input is usually just has a dummy <code>scriptSig</code>, but what if a miner used it to spend an UTXO? Would it be verified as an actual spend, or would the block be rejected?</p>
 21052: <p>It would be rejected.  The coinbase input must use a very specific previous <a href="https://bitcoin.org/en/developer-reference#raw-transaction-format" rel="nofollow">outpoint</a>: <code>0x0000000000000000000000000000000000000000000000000000000000000000ffffffff</code>. This prevents it from referring to an actual previous outpoint.</p>
