Despite all of the above, many instruction manuals for cell phone warn against overcharging. This is not because a battery can be overcharged per se, but because extended periods of incoming electrical charging may destabilize some of the battery cells.
In other words, once a battery reaches its full charge, it cannot be charged any further. At the same time, that electrical current that keeps coursing in has nowhere to go, creating a stressful electromagnetic environment and pushing the battery into more of an unknown realm. Depending on type, manufacturer and amount of time left plugged in, complications may or may not ensue.
So, yeah technically it's not overcharged. However, it will likely shorten the batteries life.