The CVS (Concurrent Versions System) software is a popular method for recording modifications to data objects, in addition to concurrent access to data in a multi-user environment. In current implementations, all users have to trust that the CVS server performs all user operations as instructed. In this paper, we develop protocols that allow users to verify that the server has been compromised, and that it has performed exactly the users? operations on the data. We first show that communication between users is necessary to guarantee that users can detect that the server has been compromised. We then propose efficient protocols that fast enable detection of server integrity under CVS workloads. Our techniques also have applications in the outsourcing model where multiple users own a common database maintained by an untrusted third-party vendor.