in the jrFollower and by extension jrFriends module there isn't a check to see if the PID exists that you are trying to follow:
So if you manually try to visit /follow/follow/[INVALID_PID] or friend/friend/[INVALID_PID] such as a PID above the int value of registered users it doesn't prevent the follow/friend attempt, will return an OK and issue a blank status update to your profile:
ViXiV
@vixiv • 2 minutes ago
@vixiv is now following @
ViXiV
@vixiv • 5 minutes ago
@vixiv is now friends with @
Customizing the error messages a bit reveals that these make it to the database as well... Upon a 2nd attempt at adding one of the same invalid PID's alerts to it already existing in DB:
{"EXISTS":1,"VALUE":"friends"}
updated by @appxprt: 07/01/17 05:12:51AM