Apple has revealed that they have found a bug in iOS 13 and iPadOS that could give full access to third party keyboards, they have also revealed that they are working on a fix for the bug.
The new iPadOS and iOS 13.1 software were both released yesterday and the fix is expected to be released quickly, you can see what they have to say about it below.
Third-party keyboard extensions in iOS can be designed to run entirely standalone, without access to external services, or they can request “full access” to provide additional features through network access. Apple has discovered a bug in iOS 13 and iPadOS that can result in keyboard extensions being granted full access even if you haven’t approved this access.
This issue does not impact Apple’s built-in keyboards. It also doesn’t impact third-party keyboards that don’t make use of full access. The issue will be fixed soon in an upcoming software update.
You can see what third party keyboard you have installed by going to Settings > General > Keyboard > Keyboards. You can find out more information about the bug over at Apple at the link below.