When a user modifies Environment Extension values, a snapshot of the extensions values along with who made the change and when is captured for comparison with previous revisions.
To view the Extension Audit Logs through the AtomSphere UI, navigate to Manage > Atom Management > select Environment > Environment Extensions > Show Audit Log.
Audit Log entries are never purged.
If you need to restore a prior extension value, use the Audit Log to view the Previous Values to compare the differences, and then re-enter the previous values into Environment Extensions click Save.
For more information see Viewing the Audit Log.
The change event is also available through the Audit Log platform API: Audit Log object