Source code synchronization is the process of ensuring that the source code and the object code (the compiled version of the source code) are consistent and up-to-date1. When program changes are implemented, the source code should be recompiled to generate a new object code that reflects the changes. However, if the source code is not recompiled, there is a risk that the object code may be outdated or incorrect. A compensating control is a measure that reduces the risk of an existing control weakness or deficiency2. A compensating control for source code synchronization is to compare the date stamping of the source and object code. Date stamping is a method of recording the date and time when a file is created or modified3. By comparing the date stamping of the source and object code, one can verify if they are synchronized or not. If the date stamping of the source code is newer than the object code, it means that the source code has been changed but not recompiled. If the date stamping of the object code is newer than the source code, it means that the object code has been compiled from a different source code. If the date stamping of both files are identical, it means that they are synchronized.

When a program release needs to be backed out of production, the changes introduced by that release must be removed from the source code to ensure the system returns to its prior state. This approach ensures that the source code reflects the stable version without the problematic changes.
References
* ISACA CISA Review Manual 27th Edition, Page 244-245 (Change Management)

The best way to enforce the principle of least privilege on a server containing data with different security classifications is to apply access controls determined by the data owner. The principle of least privilege states that users should only have the minimum level of access required to perform their tasks. The data owner is the person who has the authority and responsibility to classify, label, and protect the data according to its sensitivity and value. The data owner can define the access rights and permissions for each user or role based on the data classification policy and the business needs. This will ensure that only authorized and appropriate users can access the data and prevent unauthorized or excessive access that could compromise the confidentiality, integrity, or availability of the data. References:
* CISA Review Manual (Digital Version)
* CISA Questions, Answers & Explanations Database