iOS apps persist keychain data even after the app is deleted. For example, this allows Facebook to track you across multiple installations even if you intentionally uninstall the app.

There is no way to delete this data without jailbreak.

This can be a privacy issue that needs more awareness IMHO. Although Apple is aware of that behavior (https://forums.developer.apple.com/thread/36442)

Any thoughts?

PS: I already posted this here. Can't file a bug report. https://bugreport.apple.com/error says: 'An error has occurred'