Summary

The giveReview function uses block.timestamp for time based comparisons, which can be manipulated by miners.

Vulnerability Details

The function uses block.timestamp to enforce a time restriction between reviews:

Impact

Miners can manipulate block.timestamp to a certain degree, which allows them to slightly subvert time based restrictions. However, since the restriction is a week long, this manipulation would have minimal impact

Recommendations

I would consider using block numbers instead of timestamps. Also I would add a small buffer to account for potential timestamp manipulation