Submitted by WatchPug
Even though its unlikely in practice, but in theory, the underlying contract (EthAnchor) may suffer investment losses and causing decreasing of the PPS of AUST token. (There are codes that considered this situation in the codebase. eg. handling of depositShares > claimerShares).
However, when this happens, the late users will suffer more losses than expected than the users that withdraw earlier. The last few users may lose all their funds while the first users can get back 100% of their deposits.
When the strategy is losing money, share / underlying increases, therefore the computed depositShares: depositAmount * share / underlying will increase unexpectedly.
https://github.com/code-423n4/2022-01-sandclock/blob/a90ad3824955327597be00bb0bd183a9c228a4fb/sandclock/contracts/Vault.sol#L544-L548
While totalShares remain unchanged, but the computed depositShares is increasing, causing distortion of depositShares / totalShares, eg,  depositShares > totalShares.
In order to properly handle the investment loss of the strategy, consider adding a new storage variable called totalLoss to maintain a stable value of share / adjustedUnderlying.
CrisBRM (Sandclock) confirmed and disagreed with severity
dmvt (judge) changed severity and commented:
