The issue was addressed with improved UI handling. This issue is fixed in iOS 12.4, watchOS 5.3. A user may inadvertently complete an in-app purchase while on the lock screen.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-8682
Reference (s):
- https://support.apple.com/HT210346
- https://support.apple.com/HT210353