Vladimir Katalov of ElcomSoft:
Our latest discovery concerns synced Safari history. While researching this sync, we discovered that deleting a browsing history record makes that record disappear from synced devices; however, the record still remains available (but invisible) in iCloud. We kept researching, and discovered that such deleted records can be kept in iCloud for more than a year. We updated Elcomsoft Phone Breaker to give it the ability to extract such deleted records from the cloud. Moreover, we were able to pull additional information about Safari history entries including the exact date and time each record was last visited and deleted!
Katalov says that, since being notified, Apple is now purging records older than two weeks. Apparently, however, they’re retaining synced history items deleted within the past two weeks. I see no logical reason why records of items removed from a user’s browsing history should remain synced for any length of time.