The issue was addressed with improved UI handling. This issue is fixed in iOS 12.3. The lock screen may show a locked icon after unlocking.
https://support.apple.com/HT210118
Source: Mitre, NVD
Published: 2019-12-18
Updated: 2019-12-26
Base Score: 2.1
Vector: CVSS2#AV:L/AC:L/Au:N/C:N/I:P/A:N
Severity: Low
Base Score: 3.3
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N