Skip to main content

Infini Neobank: The Retained Developer Privilege Exploit (February 2025)

On February 24, 2025, Infini, a Hong Kong-based crypto neobank focused on stablecoin prepaid cards, was exploited for approximately $49.5 million in USDC. This incident is a definitive case of Operational Supply Chain Risk and the danger of zombie administrative roles in unverified contracts.

Technical Overview​

The exploit focused on a specialized administrative role within an unverified smart contract that had been deployed in late 2024. The contract was used to manage the treasury logic for the neobank's stablecoin reserves.

The vulnerability was not a code flaw in the traditional sense, but an Access Control persistence issue. A former developer, who had initially built the contract, retained a highly privileged role (0x8e0b) that was never revoked after their departure.

Exploit Mechanism: The Privileged Drain​

The attacker utilized their longstanding, unrevoked credentials to subvert the protocol's intended security model.

  1. Access Activation: The attacker (identified by security firms as an insider/former developer) called a privileged function in the unverified management contract using the retained key.
  2. Special Account Role: By utilizing the 0x8e0b role, the attacker granted themselves the authority to authorize a massive withdrawal of USDC from the neobank’s main vault.
  3. Treasury Siphoning: The attacker transferred 49.5 million USDC—representing nearly all value locked in the platform’s hot wallets—to a new address.
  4. Liquidation: To bypass the potential freezing of USDC by Circle, the attacker immediately swapped the funds:
    • 49.5M $USDC was swapped for 49.5M $DAI.
    • The $DAI was then used to purchase 17,696 $ETH.
    • The ETH was consolidated and moved off-chain through Tornado Cash and other mixers.

Why This Matters (The "Insider Role" Liability)​

The Infini exploit underscores a critical 2025 security realization: Privilege is a Debt.

  • Verification Gap: The use of an unverified contract concealed the existence of the special administrative role from public scrutiny and even from internal audits that did not perform deep bytecode analysis.
  • Credential Lifecycle: Most protocols focus on securing new roles and multisigs but lack a formal "Deprecation and Revocation" process for developers and contractors who leave the team.

Mitigation Strategies​

  • Forced Source Verification: Never deploy institutional treasury logic to mainnet without full source code verification on scanners like Etherscan. This allows the community and external monitors to identify "hidden" roles.
  • Role-Based Access Control (RBAC) with Multisigs: All administrative roles, even those intended for technical maintenance, MUST be managed by a decentralized multi-signature wallet (for example, Safe) rather than an EOA. This ensures no single rogue developer can initiate a drain.
  • Automated Privilege Audits: Implement weekly on-chain monitoring to inventory every address holding an administrative role. Any role held by an account not explicitly on the current personnel allowlist should trigger an automated alert.
  • Timelock for Administrative Actions: Institutional withdrawals or role modifications should undergo a mandatory Timelock period (for example, 48-72 hours), giving the team time to detect and react to an unauthorized administrative call.

Conclusion​

The $49.5M Infini incident serves as a stark reminder that the "insider threat" remains one of the most potent attack vectors in DeFi. True protocol security requires a rigid Administrative Lifecycle management—ensuring that the keys to the kingdom are not just stored in hardware, but are systematically revoked when they are no longer required.