That's not a leak, that means there is a problem with it. You may have gotten water somewhere it shouldn't be when you used the quick disconnect and pulled it out of the filter. I had mine that was dripping water from the power cord like that. I completely disassembled it and put it back together and dried out the top half. It fixed it.
my 89$ xp3's have not leaked a drop in 2 yrs ..............meanwhile my pos $ 300+ eheim 2028 pro 2 has caused me to prematurely age and get grey hair..........mini floods times 3.....broken double tap connectors....defective tops, etc, etc..............aaaaaahhhhhhhhhhh!!!!!! I am on a first name basis with eheim north america (just about)............