Bug in the JWT implementation

[sviluppomania]

Hi,
we have some problems with the JWT implementation, more details can be found in these two threads:

• https://wordpress.org/support/topic/bug-in-the-jwt-implementation-2/#post-18434405

• https://wordpress.org/support/topic/bug-in-the-jwt-implementation/#post-18432663

[sviluppomania]

@jamesdaniels
@lahirumaramba
@paulb777
@raymondlam