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Akropolis (Delphi savings pool): Flash loan + fake token reentrancy — malicious ERC20 deposit triggers re-entrant deposit() before balance update

Akropolis lost $2M DAI when an attacker exploited a reentrancy in the deposit function using a fake ERC20 token — a bug that survived reviews by three separate auditors over eight hours of repeated $50K batch attacks.

Occurred 2020-11-12 Loss $2M Status closed

Summary #

Akropolis (Delphi savings pool) suffered a Yield Aggregator / Savings Pool on 2020-11-12, resulting in a loss of approximately $2M.

What happened #

Akropolis lost $2M DAI when an attacker exploited a reentrancy in the deposit function using a fake ERC20 token — a bug that survived reviews by three separate auditors over eight hours of repeated $50K batch attacks.

Linked factors #

  • RD-F-008 — illustrative : Bug survived review (RD-F-008 = ignored disclosure; closest semantic match for audit-missed-bug) [via dashboard_risk_factors/Vulnerability in audited or unaudited code: Audited — reentrancy bug survived three audits]
  • RD-F-090 — illustrative : Mixer withdrawal → protocol interaction [via realtime_signals/Pre-exploit on-chain signals: Repeated $50K batch attacks for ~8 hours before discovery]