The settlement contract holds members' collateral. Report vulnerabilities privately through GitHub security advisories, not public issues. We aim to acknowledge reports within three days.

In scope, most severe first:

1. Withdrawing more than your available balance, or moving another member's funds.
2. Recording an obligation without the debtor's authorization.
3. Leaving a net debit uncovered so that settle fails or a balance goes negative.
4. Blocking settlement or withdrawals for other members.

Invariants the code is written to keep, and that reports should be measured against:

• balance + min(position, 0) >= 0 for every member and token, always.
• The sum of positions in a window, per token, is zero.
• Token balances held by the contract equal the sum of member balances.
• No operator action (pause, suspension, token or minimum changes) stops a member withdrawing its available balance, and no window can stay open past its bound, which cannot be unset.

src/invariants.rs checks these after every step of randomised operation sequences.

Trust in the operator, by design:

• The operator decides who may join, which tokens are allowed, and may pause new deposits and obligations or suspend a member. It cannot move funds, record obligations, or upgrade the contract: there is no upgrade function.
• The operator can settle early, which only applies positions members already authorized.

Known limits:

• Members acting together can still fill a window's 64 positions. Each member's obligations may open at most position_quota new positions per window (16 by default), so it takes at least four; set_min_amount makes it costly and set_suspended stops them.
• Only vetted tokens should be allowed: the contract calls the token's transfer on deposit and withdrawal and trusts its result.

The contract has not been audited.