It seems that SwiftKey has recently begun rolling out an update that should in theory address the issue. The rollout is going out in stages so if you don’t see it yet, don’t worry as we’re sure it will eventually get to you, so just remain patient and your keyboard app should be updated in no time at all.
For those learning about this for the first time, a couple of weeks ago, users were reporting that their SwiftKey predictions started to show numbers and email addresses that they did not recognize. It turns out that there was some kind of bug that showed some other SwiftKey user’s details to other users.
Thankfully it seems that apart from phone numbers and email addresses, nothing else major was revealed, like credit card numbers, passwords, and so on. However the company decided that the best course of action was to disable its sync services, at least until now when it has been fixed.