Security Audit Report: Reentrancy & Access Control Review: Paxos Gold

Paxos Gold (PGX) is a regulated, fiat-backed token that represents physical gold on-chain. The protocol's core contracts include PGXToken ERC-20 token, PGXBridge for L1↔L2 deposit/withdrawal, PGXController for role-based admin and upgradeability, PGXReserve for custody and audit-reporting interface, and PGXStaking (optional) for a yield-bearing staking wrapper on L2. The security audit focused on two high-impact security domains: Reentrancy and Access Control.

The audit found several vulnerabilities. In Reentrancy, the bridge's withdraw function has an external call before updating the withdrawal nonce, creating a checks-effects-interactions violation. Such an attack could allow unlimited double-spending of gold-backed tokens, leading to over-minting of PGX and a breach of the 1:1 gold peg.

Access Control issues include a public setPendingOwner function in PGXController that can be called by any address, a lack of rotation for the ownership key stored in a 3-of-5 multisig, granting the PAUSER_ROLE to a single external contract (PGXStaking), and the use of nonReentrant modifier in PGXStaking's reward-distribution loops. These issues could be exploited for Denial-of-Service attacks, rug-pulls, or hidden backdoors.

The combined risk score is 8/10, indicating a high-impact attack surface that could lead to loss of user funds or prolonged service disruption. The audit recommends adding a reentrancy guard to PGXBridge.withdraw, restricting setPendingOwner to onlyOwner, tightening the PAUSER_ROLE, rotating proxy admin multisig keys, and adding nonReentrant modifiers to external call loops in reward-distribution contracts.