A security consultant is performing an authorized assessment of a regional healthcare provider's patient portal in Portland, Oregon. During testing, he observes that authenticated users are assigned session identifiers embedded within URL parameters after login.
To evaluate the robustness of the session management implementation, he initiates multiple authentication requests in rapid succession using controlled test accounts. He then compares the issued identifiers and notices that although parts of the value remain constant, certain segments change in a predictable progression over time.
By analyzing the incremental pattern across a controlled batch of issued identifiers generated within the same time window, he is able to anticipate future valid identifiers without capturing traffic from other users.
Which token prediction mechanism best explains the weakness identified in this scenario?