functionality which not in the requirements

 It may take serious effort to determine
 if an application has significant unexpected
 or hidden functionality, and it would
 indicate deeper problems in the software
 development process. If the functionality
 isn't necessary to the purpose of the
 application, it should be removed, as
 it may have unknown impacts or dependencies
 that were not taken into account by the
 designer or the customer. If not removed,
 design information will be needed to determine
 added testing needs or regression testing needs.
 Management should be made aware of any
 significant added risks as a result of the
 unexpected functionality. If the functionality 
 only effects areas such as minor improvements
 in the user interface, for example, it may 
 not be a significant risk.