Curriculum·J305 Staking, Restaking, and Yield Architecture·about 42 min
The risk-stacking problem
By the end of this lesson you can
- →Compute the survival probability of a stack of independent layers
- →Show that yields add while failure probabilities compound, and price the asymmetry
- →Identify shared dependencies that make a stack shorter than it looks
- →Produce a layer audit that lists every party behind a position
Junior · enrolled learners
This lesson opens with Ankr and Helio, December 2022.
- What happened
- Ankr issued aBNBc, a reward-bearing token for BNB staked through its protocol. Following a technical upgrade, an attacker with what appeared to be compromised deployer privileges exploited an unlimited mint function in the aBNBc contract and minted 20 trillion tokens. The price fell about 99.5 percent, from $303.89 to $1.53, within hours. The attacker then took the minted tokens to Helio Money, a separate lending protocol that accepted aBNBc as collateral and whose price source had not yet reflected the collapse, and borrowed $16M of the HAY stablecoin against them, selling it for about $15.5M of BUSD. Ankr subsequently compensated affected liquidity providers.
- The decision point
- Three systems, each with parameters that were defensible in isolation. A staking protocol with an upgrade process. A lending protocol accepting a liquid staking token as collateral. A price source with an update interval. The failure required all three and originated in none of them jointly, because nobody was responsible for the combination. A stack is not a set of independent risks that can be multiplied. It is a set of dependencies, and a single event can traverse several of them before any one of them notices.
- Recorded loss
- $16,000,000
What you will be able to answer
- →How do failure probabilities combine across a stack?
- →What is the asymmetry between yield and risk in a stack?
- →Why is independence the wrong assumption?
- →What does a layer audit produce?
Orientation and Year One are open: anyone can read them without an account. From Year Two onward the lessons are for enrolled learners, because progress through the later years only means anything if it is tracked against a record.
It is free. We do not sell the list and there is nothing to buy at the end of it.
Sources and review
- https://www.merklescience.com/blog/hack-track-analysis-of-ankr-exploit
- https://cointelegraph.com/news/ankr-confirms-exploit-asks-for-immediate-trading-halt
- https://www.ankr.com/blog/after-action-report-our-findings-from-abnbc-token-exploit/
- https://protos.com/depeg-of-3b-restaking-token-ezeth-causes-over-60m-in-defi-liquidations/
Confidence high·Volatility medium·Reviewed 2026-08-06·Owner unassigned
Contested
The per-layer failure probabilities in the worked example are illustrative and are not estimates of any real protocol. The purpose is to show the shape of the arithmetic, which is that a small per-layer risk becomes a large stack risk while the yields only add. Substituting your own honest numbers is the exercise.
J310-06 covers stacked dependencies for tokenized real world assets, where the layers include a legal wrapper, a custodian and a redemption process running on business days. This lesson covers on-chain yield stacks. The arithmetic is the same and the layer inventory is not.