OAK — OnChain Attack Knowledge

Worked example · 2023-06

Chibi Finance panic / onlyGov residual-authority exit-scam — Arbitrum — 2023-06-27

Loss
approximately $1M drained from eight Chibi Finance protocol contracts on Arbitrum on 2023-06-27 via the deployer's panic-function admin-emergency-withdrawal path. CHIBI governance token fell ~99% on the news (some sources report "over 90%"; CoinDesk and Halborn cite ~98%). Stolen funds were swapped into 555 ETH and bridged to Ethereum, then routed through Tornado Cash. Chibi was the 12th major exit-scam recorded on Arbitrum in 2023 at the time of the incident; the broader 2023 Arbitrum exit-scam cohort had cumulatively lost >$14M to that point.
OAK Techniques observed
OAK-T1.003 (Renounced-but-not-really / Retained-Admin-Authority sub-class) — the structural enabling configuration: the deployer publicly framed Chibi as a community-governance DeFi yield-aggregator while retaining a _gov role with authority to call panic() (an emergency-withdrawal function) across all protocol contracts. OAK-T2.001 (Single-Sided Liquidity Plant — the eight Chibi Finance protocol contracts collected user-deposited assets into pools that the _gov role controlled through the panic() emergency-withdrawal path; the pools appeared to be legitimate single-asset yield vaults but were structurally operator-controlled deposit traps from deployment, with the onlyGov modifier on panic() providing the unilateral withdrawal authority) + OAK-T5.001 (Hard LP Drain / Exit Scam) — the operational outcome of weaponising the residual _gov authority. OAK-T6.001 (Source-Verification Mismatch — the protocol's public-facing communications presented a community-governance framing while the verified contract source contained the onlyGov-gated panic() emergency-withdrawal path; the gap between the public community-ownership claim and the on-chain retained-authority surface is the canonical T6.001 signal). OAK-T7.001 (Mixer-Routed Hop) — proceeds were routed through Tornado Cash for laundering, closing the recovery window structurally. The case is the canonical 2023 worked example for the onlyGov residual-authority sub-class of T1.003: the residual authority surface is documented in the verified contract source as an onlyGov modifier on a panic-style emergency function, but the public-facing protocol communications did not surface its operator-control implications.
Attribution
pseudonymous. The Chibi Finance team rebranded their Telegram and operator channels post-rug; no public attribution to a named operator group at v0.1. Per CryptoSlate's coverage, this was the 12th Arbitrum-based protocol to rug users in 2023, suggesting cohort-scale operator-recurrence even where individual cluster-attribution is not established.
Key teaching point
Chibi Finance is the canonical 2023 worked example for the onlyGov-modifier residual-authority sub-class of T1.003, structurally distinct from (a) Hope Finance's router-rerouting via retained authority (/examples/2023-02-hopefinance.md) and (b) Magnate Finance's oracle-modification via residual oracle-admin authority (/examples/2023-08-magnate-finance-base-deployer-cluster.md). The discriminating signal is the source-level onlyGov modifier: the residual authority is named in the verified contract source, gated by onlyGov rather than onlyOwner, and reachable via the deployer's ability to point _gov at a malicious contract. T1.003 contributors should treat the three sub-classes as the canonical 2023 reference triple.

Summary

Chibi Finance was a DeFi yield-aggregator on Arbitrum that publicly marketed itself as a community-governance protocol providing automatic rewards to users who staked tokens. The protocol's smart-contract architecture distributed authority across eight separate contracts, each of which exposed a panic() function gated by an onlyGov modifier — meaning the function was callable by an admin contract but not by ordinary users. The panic() function was structured as an emergency-withdrawal pathway: it withdrew all tokens from the contract's pool and sent them to a designated address.

On 2023-06-27, the Chibi Finance deployer EOA executed the rug:

  1. Transferred admin rights for the eight Chibi Finance contracts to a malicious contract under operator control. This step was legitimate at the contract layer — the deployer held the authority to assign the _gov role.
  2. The malicious _gov contract invoked panic() across all eight Chibi protocol contracts in rapid succession, executing emergency withdrawal of all funds.
  3. The drained tokens — approximately $1M aggregate value — were swapped into ETH (~555 ETH) and bridged from Arbitrum to Ethereum.
  4. The bridged ETH was routed through Tornado Cash, closing the on-chain recovery window structurally.

The CHIBI governance token's price fell ~98% as the news propagated; per Halborn's same-day analysis ("Explained: The Chibi Finance Rug Pull (June 2023)"), the rug was the 12th Arbitrum-based protocol to exit-scam users in 2023, with the cohort cumulatively losing >$14M by mid-year.

The case is OAK's canonical T1.003 example for the onlyGov residual-authority sub-class: the residual authority surface was documented in the verified contract source as an onlyGov modifier on a panic-style emergency function, and the deployer's authority to assign _gov was the load-bearing operator-control surface. The exploit was therefore not a bug — it was the intended operator-control pathway, dressed in community-governance marketing. Halborn, CertiK, Cointelegraph, CoinDesk, CryptoSlate, BeInCrypto, CryptoPotato, Tokenist, Technext, BSCN, and CoinJournal contemporaneous coverage triangulates the technical root-cause to the onlyGov panic-function pathway.

Why this is structurally significant

T1.003 has at least three structurally distinct 2023 sub-classes that share the Technique number but diverge on detection and mitigation:

  1. Router-rerouting via retained authority — Hope Finance (/examples/2023-02-hopefinance.md). The retained authority is on a router contract; the failure mode is silent token-flow redirection at runtime.

  2. onlyGov panic-function residual authority — Chibi Finance (this case). The retained authority is the deployer's ability to assign the _gov role; the panic-function is documented in the verified source. The failure mode is overt emergency-withdrawal extraction across multiple contracts.

  3. Oracle-modification via residual oracle-admin authority + cross-chain deployer cluster — Magnate Finance (/examples/2023-08-magnate-finance-base-deployer-cluster.md). The retained authority is on the lending-protocol price oracle; the failure mode is collateral-price inflation followed by lending-pool drainage; M04 cluster-attribution is the canonical defender-tooling primitive.

The three sub-classes share the structural property that the residual authority surface was checkable on-chain at the contract layer before the rug, but they require different detection methodologies:

  • Hope: bytecode review + proxy-implementation analysis on Arbiscan.
  • Chibi: verified-source review + role-assignment privilege graph (M05 authority-graph enumeration).
  • Magnate: M04 funder-graph clustering + cross-chain deployer-EOA correlation.

Chibi's structural distinguishing feature is that the residual authority was named in the source code and visible in the verified Etherscan / Arbiscan contract. The defender did not need to recompile bytecode (Hope) or trace cross-chain deployer linkage (Magnate); the panic() function gated by onlyGov was readable in plain Solidity. The case is therefore a particularly clean teaching example for the source-level authority-graph enumeration mitigation pattern (OAK-M05).

Three structural features distinguish the case within the T1.003 cohort:

  1. The residual authority is multi-contract. Eight separate Chibi Finance contracts each exposed a panic() function gated by the same onlyGov modifier. The deployer's single _gov reassignment unlocked the panic pathway across all eight contracts simultaneously. T1.003 detection methodology should enumerate the residual-authority surface across the protocol's full contract graph, not just on the headline contract.

  2. The Tornado Cash recovery-window-closure is the standard 2023 endpoint. Chibi's proceeds reached Tornado Cash within hours of the rug; standard recovery-window-closure profile across the 2023 T1.003 cohort. The structural property is shared with Hope Finance, Magnate Finance, and the broader 2023 rug-pull cohort whose proceeds reach a public mixer in the same transaction window.

  3. The Arbitrum-2023 cohort scale. Chibi was the 12th Arbitrum-based exit-scam in 2023; the cohort cumulatively lost >$14M by mid-year. The chain-distribution is a gas-economics signal (cheap deployment + active retail capital + young listing-compliance regimes); future T1.003 examples should record the chain-cohort context.

Timeline (UTC)

When Event OAK ref
Pre-2023-06 Chibi Finance launches on Arbitrum as DeFi yield-aggregator; publicly markets community-governance framing; deploys eight protocol contracts each gated by onlyGov panic() modifier; _gov role assignable by deployer (T1.003 standing surface)
2023-06-27 Deployer transfers _gov admin rights for the eight Chibi Finance contracts to a malicious contract under operator control T1.003 setup (residual-authority-reassignment)
2023-06-27 (same window) Malicious _gov contract invokes panic() across all eight Chibi protocol contracts in rapid succession; emergency-withdrawal extracts ~$1M aggregate T1.003 + T5.001 execution
2023-06-27 (within hours) Drained tokens swapped into ~555 ETH; bridged from Arbitrum to Ethereum T5 outflow
2023-06-27 (within hours) CHIBI token falls ~98% as news propagates; CertiK, Halborn, Cointelegraph, CoinDesk publish forensic coverage (defender response / market signal)
2023-06-27 onward Bridged ETH routed through Tornado Cash; on-chain trail effectively foreclosed at the mixer boundary T7.001
Continuing No public recovery; no civil-forfeiture action; operators remain pseudonymous (recovery state)

What defenders observed

  • Pre-event (verified-source layer): the panic() function gated by onlyGov was named in the verified contract source on Arbiscan. A standard source-level review (OAK-M05 authority-graph enumeration) would have surfaced the residual authority across the eight protocol contracts. Defender lesson: source-level review of every authority-bearing modifier across the protocol's full contract graph is the canonical 2023 mitigation pattern; the residual authority was hiding in plain sight, not behind proxy indirection or bytecode obfuscation.
  • At-event (role-assignment signal): the deployer's transfer of _gov to the malicious contract is a single transaction event observable on Arbiscan. A protocol-monitoring indexer subscribed to _gov role-assignment events would have detected the precondition; the malicious _gov contract's subsequent panic() calls are the extraction signal. Vendor coverage of this monitoring pattern at v0.1 is partial; v0.x mitigation work should formalise the integration pattern at the wallet / venue UX layer.
  • At-event (CHIBI-price signal): the governance token fell ~98% as the news propagated; a price-surface indexer integrated with on-chain monitoring would have flagged the rug within minutes. The price signal is secondary to the on-chain extraction signal but operationally useful for cohort-scale alerting.
  • Post-event: standard Tornado-Cash recovery-window-closure profile. Within hours of the rug, proceeds had reached the mixer and the on-chain trail was effectively foreclosed at the mixer boundary. The base-rate expectation for T1.003 / T5.001 incidents whose proceeds reach a mixer within the same operational window is total loss with no recovery; Chibi is consistent with the base rate.

What this example tells contributors writing future Technique pages

  • T1.003 has at least three structurally distinct 2023 sub-classes. Hope Finance (router-rerouting), Chibi Finance (this case, onlyGov residual authority), Magnate Finance (oracle-modification + cross-chain cluster). The three together cover the canonical 2023 T1.003 reference triple. T1.003 contributors should preserve the sub-class distinction; the detection methodology diverges across the three.
  • Multi-contract authority-graph enumeration is the load-bearing M05 pattern. Chibi's residual authority spanned eight protocol contracts; a single-contract review would have missed the full extraction surface. M05 enumeration must cover the protocol's full contract graph, not just the headline contract.
  • Source-level review of onlyGov / onlyAdmin / onlyEmergency modifiers is the canonical 2023 defender practice. Chibi's panic() function was named in the verified source; the residual authority was not hiding behind proxy indirection. Defender practice should treat every authority-bearing modifier across the protocol's full contract graph as a residual-authority surface until proven gated by timelocked governance.
  • The Tornado Cash recovery-window-closure is the standard 2023 endpoint. Future T1.003 examples should record whether proceeds reached a public mixer within the same operational window; if so, the recovery-window is structurally foreclosed and the defender intervention surface narrows to forward-going user exposure.
  • Cohort-scale chain-distribution is a gas-economics signal. Chibi was the 12th Arbitrum-based exit-scam in 2023; cohort-scale chain-distribution is informative for defender-tooling prioritisation. Future T1.003 examples should record the chain-cohort context.

Public references

Discussion

Chibi Finance is OAK's canonical 2023 worked example for the onlyGov residual-authority sub-class of T1.003. The structural distinguishing feature is that the residual authority surface was named in the verified contract source — the panic() function gated by onlyGov is readable in plain Solidity on Arbiscan. The case is therefore a particularly clean teaching example for the source-level authority-graph enumeration mitigation pattern (OAK-M05): the residual authority was hiding in plain sight, not behind proxy indirection or bytecode obfuscation. Defenders performing standard source-level review of every authority-bearing modifier across the protocol's full contract graph would have surfaced the residual authority pre-rug.

The case structurally complements Hope Finance (/examples/2023-02-hopefinance.md — router-rerouting via retained authority) and Magnate Finance (/examples/2023-08-magnate-finance-base-deployer-cluster.md new — oracle-modification via residual oracle-admin authority + cross-chain deployer cluster). The three together cover the canonical 2023 T1.003 sub-pattern reference triple.

For OAK's broader cohort coverage at v0.1, the Chibi case is the cleanest single-chain (Arbitrum) T1.003 example with multi-source forensic triangulation (Halborn, CertiK, Cointelegraph, CoinDesk, CryptoSlate, BeInCrypto, BSCN, Tokenist, CryptoPotato, Coin Journal, Technext); meets the v0.1 standard for "verified across at least 2 independent forensic providers" with substantial margin. The case anchors the v0.1 T1.003 example set as the source-level-readable sub-class, distinct from the bytecode-review (Hope) and cluster-attribution (Magnate) sub-classes.

Techniques demonstrated (5)