Leaks somewhere in radiator system?

Yep." Its important to find it asap that said its great that you can see it that a good start. And remember wherever it starts can be a bit higher than where you see it. Also it can be leaking in one place on the eng a travel over and continue down and exit onto the ground in anothe place so get a good light and a mechanics mirror and youl eventually find its origin. Heres a few places you might try looking
. Wherever there appears to be a parting line like between the cylinder head and the block or under the intake manifold where it fastens to the cylinder head hose joints pipe joints and so on if you see it try to follow it upwards to were it started and many times it can be a pin hole sqirting coolant accros to another area of the engine and then dripping down to appear as if its coming from that area also it can be leaking from the coolant pump and rout from under a cover use good meathodology by focusing on sections of the engine . Front. Sides and back like that one section at a time helps alot somtimes. Dont be fooled. Good luck hope this helps.

Also is the check engine light on? If it is have it scanned to retrieve the codes. Change the thermostat for sure if you havent yet. And also Keep in mind the engine can also be leaking internally as well. But since you said you see it leaking out the back if you meen somwhere out the back of the engine /under the hood then thers a good chance its somting pretty simple to repair but if your seeing it out the back of the exhuast pipe thats no good might be a blown head gasket or a cracked part hope not. Best of luck "