A Single Coinbase Price Feed Triggered $110 Million in Compound Liquidations

On November 26, 2020, a wave of liquidations swept through Compound Finance after the price feed the protocol relied on - an oracle operated by Coinbase - reported a sharp and apparently erroneous price move. The episode, part of a broader run of exploits during what REKT has called a 2020 "hack epidemic", highlights a persistent problem in DeFi: every price oracle, on-chain or off-chain, requires some form of trust, and that trust can fail.

As researcher samczsun has written, protocols building price oracles generally choose between two designs. They can take existing off-chain price data from APIs or exchanges and post it on-chain, or they can calculate an instantaneous price by querying on-chain decentralized exchanges directly. Each approach carries tradeoffs. On-chain oracles - built on platforms such as Uniswap, Kyber, or Balancer - require no privileged access and stay continuously current, but that same openness makes them comparatively easy to manipulate. Off-chain oracles, such as the one Coinbase runs, react more slowly to volatility, but introduce a different weakness: a privileged party has to push the data on-chain, meaning users must trust that party not to act maliciously, and not to be coerced into publishing bad updates.

On November 26, that trust arrangement broke down - whether through error or manipulation is still not established. The Coinbase oracle reported DAI spiking to $1.30, and Compound, which used Coinbase as its sole source for that price, registered the DAI/USDC pair as having come off its peg. The result was a cascade of loan liquidations totaling more than $110 million, and sizeable profits for the parties positioned to execute them.

Trader Sam Priestley documented one such liquidation in detail: a Compound user running a leveraged position - lending and borrowing both DAI and USDC - was liquidated for $49 million, with the liquidator earning $3.7 million simply for calling the liquidation function. Because DAI's reported price moved, the account crossed into liquidation territory; Priestley noted that keeping DAI and USDC holdings in separate wallets would have avoided this outcome. Once liquidation triggered, the liquidator could choose which collateral to seize. They took DAI, borrowed DAI from Uniswap to repay the user's DAI debt, then used the DAI obtained from the liquidation itself to repay the Uniswap loan and keep the difference as profit. Priestley added that the user may have assumed their USDC was uninvolved because they had never directly called the "enter-markets" function on it - but by borrowing USDC against the position, they had inadvertently activated it as collateral for the DAI debt as well.

DAI's price move over this period was described as a dramatic swing for an asset designed to hold a stable value.

When Coinbase introduced its price oracle, the exchange acknowledged the built-in tradeoff of an off-chain source: it requires trusting the publisher to post correct prices and to safeguard its signing key. Rather than proposing measures to reduce that reliance on trust, the announcement instead argued that Coinbase's standing made it a suitable party to trust, calling itself "one of the most trusted companies in the crypto space" and framing a Coinbase-anchored feed as a way to make DeFi "safer" and cut "systemic risks." Compound co-founder and CEO Robert Leshner echoed that framing at the time, stating that the Coinbase oracle would "increase the security and decentralization of Compound's price feed."

Whether the November 26 incident stemmed from a technical fault or deliberate manipulation remains unclear. Coinbase's own status page has previously logged unspecified "issues" affecting the oracle. What is established is that no flash loans were used in the event: pushing the relevant Coinbase order book off balance to the degree observed would have required roughly 100,000 DAI, given that the book held about 300,000 DAI of depth at the time - enough to drive the reported price to $1.30.

Regardless of whether the cause was malicious action, negligence, or a technical failure, the liquidation bots that acted on the resulting price data profited all the same. The incident underscores the risks of relying on any single centralized source for a price oracle - a risk this episode suggests is especially pronounced for Coinbase's feed, given that its order book could reportedly be pushed off balance with a comparatively modest 100,000 DAI.