Rear Door Window is Loose

[Trob20]

I noticed recently my driver's side rear door window is loose. When I hit a bump while driving you can hear it jump, and I was also able to move the window up & down and side to side with my hand. Is this a problem? If this is a problem, what can I do about it?

 

[BlackWorksInc]

First thing is first, pop off the door panel and see if the bolts that secure the glass to the regulator are tight (common issue among many cars,) or if the regulator itself is failing and will need to be replaced.