CVE-2019-11272: PlaintextPasswordEncoder authenticates encoded passwords that are null

Spring Security, versions 4.2.x up to 4.2.12, and older unsupported versions support plain text passwords using PlaintextPasswordEncoder. If an application using an affected version of Spring Security is leveraging PlaintextPasswordEncoder and a user has a null encoded password, a malicious user (or attacker) can authenticate using a password of "null".