Incident Overview
The USM protocol suffered an exploit due to a pricing logic flaw in the ethFromDefund() function within defund(). It uses the arithmetic mean of the current and estimated final FUM sell prices for a single redemption but lacks “split invariance.” Combined with the per-redemption state contraction (adjShrinkFactor) and integer rounding, an attacker used a flash loan to call fund() to manipulate internal pricing, then split the same FUM amount into 64 small defund() calls, extracting more ETH than a single large call and causing a loss of ~70.83 ETH.
Sources & References
This record presents information attributed to the linked sources. Incident dates describe the original event, not a new report. Reported loss figures reflect the source record and are not current market valuations.