Summary

No mechanism for the seller to negotiate a higher payment.

Vulnerability Details

initiateDispute name suggests that if the two parties don't agree on something (i.e. the payment amount)
they rely on a third party to resolve the conflict. If the seller would want a higher payment for the service, he calls the initiateDispute function, but what happens next is that in resolveDispute the arbiter fee and buyerAward will be deducted from the initial payment.

Impact

The seller must give the service according to the set price, and there is no way he can actually negotiate the price.

Tools Used

Manual Review

Recommendations

There should be a mechanism for the seller to set a higher payment amount in the initiateDispute function.