Submitted by BenRai, also found by NexusAudits and seerether
https://github.com/code-423n4/2024-12-secondswap/blob/b9497bcf5100046a169276cb6b351ebc0eddc2cc/contracts/SecondSwap_VestingManager.sol#L194-L198
https://github.com/code-423n4/2024-12-secondswap/blob/b9497bcf5100046a169276cb6b351ebc0eddc2cc/contracts/SecondSwap_VestingManager.sol#L179
This issue allows the maxSellPercent to be increased to 20% against the will of the token issuer. This will result in users being able to sell tokens even when the issuer intended to prevent selling.
The SecondSwap_VestingManager contract manages vesting settings and allocations for tokens. A critical function in this context is setMaxSellPercent, which allows the tokenIssuer to set the maximum percentage of vesting tokens that can be sold by users. 
The issue arises from the interaction between the setSellable and setMaxSellPercent functions. When the tokenIssuer sets maxSellPercent to 0 to prevent selling, the following sequence of events can occur:
This flaw allows the admin to accidentally override the issuers settings, leading to unauthorized selling of tokens.
It also sets the sellFee and buyFee back to default which might not be intended if the admit has changed them before.
To mitigate this issue, a new variable initiated should be added to the vesting settings. This variable will track whether the vesting has been initialized. The setSellable function should only update the maxSellPercent if initiated is false which should only be when the vesting is initial created.
bobwong (SecondSwap) confirmed
