Keyboard app Swiftkey is incredibly popular, thanks mainly to its artificial intelligence prediction engine that's able to suggest the next word, or even emoji, you may want to use. But the company has suspended some of its services after a data leak caused predictions meant for other people to appear on users' phones. The suggestions included emails, phone numbers, and even pornographic search terms.

"This week, a few of our customers noticed unexpected predictions where unfamiliar terms, and in some rare cases emails, appeared when using their mobile phone. We are working quickly to resolve this inconvenience," wrote Swiftkey in a blog post.

Swiftkey said the problem was likely due to a glitch in its cloud syncing service, which backs up individual users' predictions on the company's servers so the information can be synced to customers' other devices.

Affected users have reported strangers' email addresses, contact details, and search terms, along with words not from their selected language, appearing as predictions.

"A few days ago, I received an email from a complete stranger asking if I had recently purchased and returned a particular model of mobile phone, adding that not one but two of my email addresses (one personal and one work address) were saved on the phone she had just bought as brand new," one user told the Telegraph.

Swiftkey insists that the issue did not pose a security issue, but said it has turned off the cloud sync service and updated its applications to remove email address predictions as a precaution. The company assured people that the app is "okay to use" in the meantime and that their personal data is safe.

"The vast majority of SwiftKey users are not affected by this issue. If you have any reason to believe you are seeing unfamiliar predictions, please contact," the company wrote.

Swiftkey has been installed on more than 300 million devices worldwide. Microsoft was so impressed with the AI technology behind the software that it paid $250 million to acquire the firm earlier this year.