  We study an auction with $m$ identical items in a context where $n$ agents
can arbitrarily commit to strategies. In general, such commitments
non-trivially change the equilibria by inducing a metagame of choosing which
strategies to commit to. In this model, we demonstrate a strategy that an
attacker may commit to that ensures they receive one such item for free, while
forcing the remaining agents to enter into a lottery for the remaining items
(albeit for free). The attack is thus detrimental to the auctioneer who loses
most of their revenue. For various types of auctions that are not too
congested, we show that the strategy works as long as the agents have
valuations that are somewhat concentrated. In this case, all agents will
voluntarily cooperate with the attacker to enter into the lottery, because
doing so gives them a chance of receiving a free item that would have otherwise
cost an amount commensurate with their valuation. The attack is robust to a
large constant fraction of the agents being either oblivious to the attack or
having exceptionally high valuations (thus reluctant to enter into the
lottery). For these agents, the attacker may coerce them into cooperating by
promising them a free item rather than entering in to the lottery. We show that
the conditions for the attack to work hold with high probability when (1) the
auction is not too congested, and (2) the valuations are sampled i.i.d. from
either a uniform distribution or a Pareto distribution. The attack works for
first-price auctions, second-price auctions and the transaction fee mechanism
EIP-1559 used by the Ethereum blockchain.

Computer Science and Game Theory