  We identify a subtle security issue that impacts mechanism design in
scenarios in which agents can absolutely commit to strategies. Absolute
commitments allow the strategy of an agent to depend on the commitments made by
the other agents. This changes fundamental game-theoretic assumptions by
inducing a meta-game in which agents choose which strategies they commit to.
  We say that a game that is unaffected by such commitments is Stackelberg
resilient and show that computing it is intractible in general, although it can
be computed efficiently for two-player games of perfect information. We show
the intuitive, but technically non-trivial result, that, if a game is resilient
when some number of players have the capacity to make commitments, it is also
resilient when these commitments are available to fewer players. We demonstrate
the non-triviality of Stackelberg resilience by analyzing two escrow mechanisms
from the literature. These mechanisms have the same intended functionality, but
we show that only one is Stackelberg resilient.
  Our model is particularly relevant in Web3 scenarios, where these absolute
commitments can be realized by the automated and irrevocable nature of smart
contracts. Our work highlights an important issue in ensuring the secure design
of Web3. In particular, our work suggests that smart contracts already deployed
on major blockchains may be susceptible to these attacks.
