JJWT (aka Java JWT) up to and including 0.12.5 ignores certain characters and thus a user might falsely conclude that they have a strong key. The impacted code is the setSigningKey() method within the DefaultJwtParser class and the signWith() method within the DefaultJwtBuilder class. NOTE: the vendor disputes this because the "ignores" behavior cannot occur (in any version) unless there is a user error in how JJWT is used, and because the version that was actually tested must have been more than six years out of date.
Vulmon