This BattleEye exploit demonstrates a classic failure of trust boundary definition - they effectively created a system where client attestation was accepted without proper authentication or verification.
Can you elaborate? I'm unsure what a trust boundary definition means in this context and how it relates to attestation.
Trusting something outside of your control is a good example. When your trusted game server trusts the untrusted game client when it says "trust me, it was a headshot" without validating this.