Submitted by minhquanym
In the Opus protocol, the absorber is a stability pool that permits yin holders to contribute their yin and participate in liquidations (also known as absorptions) as a consolidated pool. Provided yin from users could be absorbed during an absorption. In return, users receive yang, which usually has a higher value than the absorbed yin. However, in the event of bad debt, it could be less. This situation could lead to risk-free yield frontrunning tactics, where an attacker only provides yin when the absorption brings profit then removing all yin right after that.
The Opus team is aware of this attack vector and has, therefore, implemented a request-withdraw procedure. Users must first request a withdrawal and wait for a certain period before executing the withdrawal.
However, the provide() method does not reset these request timestamps, which allows an attacker to bypass this safeguard.
The attackers tactics will be:
Reset the withdrawal request in the provide() function.
MEV
tserg (Opus) confirmed, but disagreed with severity and commented:
0xsomeone (judge) decreased severity to Medium and commented:
Note: For full discussion, see here.
